linux/virt/kvm/kvm_main.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel-based Virtual Machine driver for Linux
 *
 * This module enables machines with Intel VT-x extensions to run virtual
 * machines without emulation or binary translation.
 *
 * Copyright (C) 2006 Qumranet, Inc.
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * Authors:
 *   Avi Kivity   <avi@qumranet.com>
 *   Yaniv Kamay  <yaniv@qumranet.com>
 */

#include <kvm/iodev.h>

#include <linux/kvm_host.h>
#include <linux/kvm.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/percpu.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/vmalloc.h>
#include <linux/reboot.h>
#include <linux/debugfs.h>
#include <linux/highmem.h>
#include <linux/file.h>
#include <linux/syscore_ops.h>
#include <linux/cpu.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/sched/stat.h>
#include <linux/cpumask.h>
#include <linux/smp.h>
#include <linux/anon_inodes.h>
#include <linux/profile.h>
#include <linux/kvm_para.h>
#include <linux/pagemap.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/compat.h>
#include <linux/srcu.h>
#include <linux/hugetlb.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/bsearch.h>
#include <linux/io.h>
#include <linux/lockdep.h>
#include <linux/kthread.h>
#include <linux/suspend.h>

#include <asm/processor.h>
#include <asm/ioctl.h>
#include <linux/uaccess.h>

#include "coalesced_mmio.h"
#include "async_pf.h"
#include "kvm_mm.h"
#include "vfio.h"

#define CREATE_TRACE_POINTS
#include <trace/events/kvm.h>

#include <linux/kvm_dirty_ring.h>

/* Worst case buffer size needed for holding an integer. */
#define ITOA_MAX_LEN 12

MODULE_AUTHOR("Qumranet");
MODULE_LICENSE("GPL");

/* Architectures should define their poll value according to the halt latency */
unsigned int halt_poll_ns = KVM_HALT_POLL_NS_DEFAULT;
module_param(halt_poll_ns, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns);

/* Default doubles per-vcpu halt_poll_ns. */
unsigned int halt_poll_ns_grow = 2;
module_param(halt_poll_ns_grow, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_grow);

/* The start value to grow halt_poll_ns from */
unsigned int halt_poll_ns_grow_start = 10000; /* 10us */
module_param(halt_poll_ns_grow_start, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_grow_start);

/* Default resets per-vcpu halt_poll_ns . */
unsigned int halt_poll_ns_shrink;
module_param(halt_poll_ns_shrink, uint, 0644);
EXPORT_SYMBOL_GPL(halt_poll_ns_shrink);

/*
 * Ordering of locks:
 *
 *	kvm->lock --> kvm->slots_lock --> kvm->irq_lock
 */

DEFINE_MUTEX(kvm_lock);
static DEFINE_RAW_SPINLOCK(kvm_count_lock);
LIST_HEAD(vm_list);

static cpumask_var_t cpus_hardware_enabled;
static int kvm_usage_count;
static atomic_t hardware_enable_failed;

static struct kmem_cache *kvm_vcpu_cache;

static __read_mostly struct preempt_ops kvm_preempt_ops;
static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);

struct dentry *kvm_debugfs_dir;
EXPORT_SYMBOL_GPL(kvm_debugfs_dir);

static const struct file_operations stat_fops_per_vm;

static struct file_operations kvm_chardev_ops;

static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
			   unsigned long arg);
#ifdef CONFIG_KVM_COMPAT
static long kvm_vcpu_compat_ioctl(struct file *file, unsigned int ioctl,
				  unsigned long arg);
#define KVM_COMPAT(c)	.compat_ioctl	= (c)
#else
/*
 * For architectures that don't implement a compat infrastructure,
 * adopt a double line of defense:
 * - Prevent a compat task from opening /dev/kvm
 * - If the open has been done by a 64bit task, and the KVM fd
 *   passed to a compat task, let the ioctls fail.
 */
static long kvm_no_compat_ioctl(struct file *file, unsigned int ioctl,
				unsigned long arg) { return -EINVAL; }

static int kvm_no_compat_open(struct inode *inode, struct file *file)
{
	return is_compat_task() ? -ENODEV : 0;
}
#define KVM_COMPAT(c)	.compat_ioctl	= kvm_no_compat_ioctl,	\
			.open		= kvm_no_compat_open
#endif
static int hardware_enable_all(void);
static void hardware_disable_all(void);

static void kvm_io_bus_destroy(struct kvm_io_bus *bus);

__visible bool kvm_rebooting;
EXPORT_SYMBOL_GPL(kvm_rebooting);

#define KVM_EVENT_CREATE_VM 0
#define KVM_EVENT_DESTROY_VM 1
static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
static unsigned long long kvm_createvm_count;
static unsigned long long kvm_active_vms;

static DEFINE_PER_CPU(cpumask_var_t, cpu_kick_mask);

__weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
						   unsigned long start, unsigned long end)
{
}

__weak void kvm_arch_guest_memory_reclaimed(struct kvm *kvm)
{
}

bool kvm_is_zone_device_pfn(kvm_pfn_t pfn)
{
	/*
	 * The metadata used by is_zone_device_page() to determine whether or
	 * not a page is ZONE_DEVICE is guaranteed to be valid if and only if
	 * the device has been pinned, e.g. by get_user_pages().  WARN if the
	 * page_count() is zero to help detect bad usage of this helper.
	 */
	if (!pfn_valid(pfn) || WARN_ON_ONCE(!page_count(pfn_to_page(pfn))))
		return false;

	return is_zone_device_page(pfn_to_page(pfn));
}

bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
{
	/*
	 * ZONE_DEVICE pages currently set PG_reserved, but from a refcounting
	 * perspective they are "normal" pages, albeit with slightly different
	 * usage rules.
	 */
	if (pfn_valid(pfn))
		return PageReserved(pfn_to_page(pfn)) &&
		       !is_zero_pfn(pfn) &&
		       !kvm_is_zone_device_pfn(pfn);

	return true;
}

/*
 * Switches to specified vcpu, until a matching vcpu_put()
 */
void vcpu_load(struct kvm_vcpu *vcpu)
{
	int cpu = get_cpu();

	__this_cpu_write(kvm_running_vcpu, vcpu);
	preempt_notifier_register(&vcpu->preempt_notifier);
	kvm_arch_vcpu_load(vcpu, cpu);
	put_cpu();
}
EXPORT_SYMBOL_GPL(vcpu_load);

void vcpu_put(struct kvm_vcpu *vcpu)
{
	preempt_disable();
	kvm_arch_vcpu_put(vcpu);
	preempt_notifier_unregister(&vcpu->preempt_notifier);
	__this_cpu_write(kvm_running_vcpu, NULL);
	preempt_enable();
}
EXPORT_SYMBOL_GPL(vcpu_put);

/* TODO: merge with kvm_arch_vcpu_should_kick */
static bool kvm_request_needs_ipi(struct kvm_vcpu *vcpu, unsigned req)
{
	int mode = kvm_vcpu_exiting_guest_mode(vcpu);

	/*
	 * We need to wait for the VCPU to reenable interrupts and get out of
	 * READING_SHADOW_PAGE_TABLES mode.
	 */
	if (req & KVM_REQUEST_WAIT)
		return mode != OUTSIDE_GUEST_MODE;

	/*
	 * Need to kick a running VCPU, but otherwise there is nothing to do.
	 */
	return mode == IN_GUEST_MODE;
}

static void ack_flush(void *_completed)
{
}

static inline bool kvm_kick_many_cpus(struct cpumask *cpus, bool wait)
{
	if (cpumask_empty(cpus))
		return false;

	smp_call_function_many(cpus, ack_flush, NULL, wait);
	return true;
}

static void kvm_make_vcpu_request(struct kvm_vcpu *vcpu, unsigned int req,
				  struct cpumask *tmp, int current_cpu)
{
	int cpu;

	if (likely(!(req & KVM_REQUEST_NO_ACTION)))
		__kvm_make_request(req, vcpu);

	if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
		return;

	/*
	 * Note, the vCPU could get migrated to a different pCPU at any point
	 * after kvm_request_needs_ipi(), which could result in sending an IPI
	 * to the previous pCPU.  But, that's OK because the purpose of the IPI
	 * is to ensure the vCPU returns to OUTSIDE_GUEST_MODE, which is
	 * satisfied if the vCPU migrates. Entering READING_SHADOW_PAGE_TABLES
	 * after this point is also OK, as the requirement is only that KVM wait
	 * for vCPUs that were reading SPTEs _before_ any changes were
	 * finalized. See kvm_vcpu_kick() for more details on handling requests.
	 */
	if (kvm_request_needs_ipi(vcpu, req)) {
		cpu = READ_ONCE(vcpu->cpu);
		if (cpu != -1 && cpu != current_cpu)
			__cpumask_set_cpu(cpu, tmp);
	}
}

bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
				 unsigned long *vcpu_bitmap)
{
	struct kvm_vcpu *vcpu;
	struct cpumask *cpus;
	int i, me;
	bool called;

	me = get_cpu();

	cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
	cpumask_clear(cpus);

	for_each_set_bit(i, vcpu_bitmap, KVM_MAX_VCPUS) {
		vcpu = kvm_get_vcpu(kvm, i);
		if (!vcpu)
			continue;
		kvm_make_vcpu_request(vcpu, req, cpus, me);
	}

	called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
	put_cpu();

	return called;
}

bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
				      struct kvm_vcpu *except)
{
	struct kvm_vcpu *vcpu;
	struct cpumask *cpus;
	unsigned long i;
	bool called;
	int me;

	me = get_cpu();

	cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
	cpumask_clear(cpus);

	kvm_for_each_vcpu(i, vcpu, kvm) {
		if (vcpu == except)
			continue;
		kvm_make_vcpu_request(vcpu, req, cpus, me);
	}

	called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
	put_cpu();

	return called;
}

bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
{
	return kvm_make_all_cpus_request_except(kvm, req, NULL);
}
EXPORT_SYMBOL_GPL(kvm_make_all_cpus_request);

#ifndef CONFIG_HAVE_KVM_ARCH_TLB_FLUSH_ALL
void kvm_flush_remote_tlbs(struct kvm *kvm)
{
	++kvm->stat.generic.remote_tlb_flush_requests;

	/*
	 * We want to publish modifications to the page tables before reading
	 * mode. Pairs with a memory barrier in arch-specific code.
	 * - x86: smp_mb__after_srcu_read_unlock in vcpu_enter_guest
	 * and smp_mb in walk_shadow_page_lockless_begin/end.
	 * - powerpc: smp_mb in kvmppc_prepare_to_enter.
	 *
	 * There is already an smp_mb__after_atomic() before
	 * kvm_make_all_cpus_request() reads vcpu->mode. We reuse that
	 * barrier here.
	 */
	if (!kvm_arch_flush_remote_tlb(kvm)
	    || kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
		++kvm->stat.generic.remote_tlb_flush;
}
EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
#endif

static void kvm_flush_shadow_all(struct kvm *kvm)
{
	kvm_arch_flush_shadow_all(kvm);
	kvm_arch_guest_memory_reclaimed(kvm);
}

#ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
					       gfp_t gfp_flags)
{
	gfp_flags |= mc->gfp_zero;

	if (mc->kmem_cache)
		return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
	else
		return (void *)__get_free_page(gfp_flags);
}

int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min)
{
	void *obj;

	if (mc->nobjs >= min)
		return 0;
	while (mc->nobjs < ARRAY_SIZE(mc->objects)) {
		obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT);
		if (!obj)
			return mc->nobjs >= min ? 0 : -ENOMEM;
		mc->objects[mc->nobjs++] = obj;
	}
	return 0;
}

int kvm_mmu_memory_cache_nr_free_objects(struct kvm_mmu_memory_cache *mc)
{
	return mc->nobjs;
}

void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
{
	while (mc->nobjs) {
		if (mc->kmem_cache)
			kmem_cache_free(mc->kmem_cache, mc->objects[--mc->nobjs]);
		else
			free_page((unsigned long)mc->objects[--mc->nobjs]);
	}
}

void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
{
	void *p;

	if (WARN_ON(!mc->nobjs))
		p = mmu_memory_cache_alloc_obj(mc, GFP_ATOMIC | __GFP_ACCOUNT);
	else
		p = mc->objects[--mc->nobjs];
	BUG_ON(!p);
	return p;
}
#endif

static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
{
	mutex_init(&vcpu->mutex);
	vcpu->cpu = -1;
	vcpu->kvm = kvm;
	vcpu->vcpu_id = id;
	vcpu->pid = NULL;
#ifndef __KVM_HAVE_ARCH_WQP
	rcuwait_init(&vcpu->wait);
#endif
	kvm_async_pf_vcpu_init(vcpu);

	kvm_vcpu_set_in_spin_loop(vcpu, false);
	kvm_vcpu_set_dy_eligible(vcpu, false);
	vcpu->preempted = false;
	vcpu->ready = false;
	preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
	vcpu->last_used_slot = NULL;
}

static void kvm_vcpu_destroy(struct kvm_vcpu *vcpu)
{
	kvm_arch_vcpu_destroy(vcpu);
	kvm_dirty_ring_free(&vcpu->dirty_ring);

	/*
	 * No need for rcu_read_lock as VCPU_RUN is the only place that changes
	 * the vcpu->pid pointer, and at destruction time all file descriptors
	 * are already gone.
	 */
	put_pid(rcu_dereference_protected(vcpu->pid, 1));

	free_page((unsigned long)vcpu->run);
	kmem_cache_free(kvm_vcpu_cache, vcpu);
}

void kvm_destroy_vcpus(struct kvm *kvm)
{
	unsigned long i;
	struct kvm_vcpu *vcpu;

	kvm_for_each_vcpu(i, vcpu, kvm) {
		kvm_vcpu_destroy(vcpu);
		xa_erase(&kvm->vcpu_array, i);
	}

	atomic_set(&kvm->online_vcpus, 0);
}
EXPORT_SYMBOL_GPL(kvm_destroy_vcpus);

#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
{
	return container_of(mn, struct kvm, mmu_notifier);
}

static void kvm_mmu_notifier_invalidate_range(struct mmu_notifier *mn,
					      struct mm_struct *mm,
					      unsigned long start, unsigned long end)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);
	int idx;

	idx = srcu_read_lock(&kvm->srcu);
	kvm_arch_mmu_notifier_invalidate_range(kvm, start, end);
	srcu_read_unlock(&kvm->srcu, idx);
}

typedef bool (*hva_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range);

typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start,
			     unsigned long end);

typedef void (*on_unlock_fn_t)(struct kvm *kvm);

struct kvm_hva_range {
	unsigned long start;
	unsigned long end;
	pte_t pte;
	hva_handler_t handler;
	on_lock_fn_t on_lock;
	on_unlock_fn_t on_unlock;
	bool flush_on_ret;
	bool may_block;
};

/*
 * Use a dedicated stub instead of NULL to indicate that there is no callback
 * function/handler.  The compiler technically can't guarantee that a real
 * function will have a non-zero address, and so it will generate code to
 * check for !NULL, whereas comparing against a stub will be elided at compile
 * time (unless the compiler is getting long in the tooth, e.g. gcc 4.9).
 */
static void kvm_null_fn(void)
{

}
#define IS_KVM_NULL_FN(fn) ((fn) == (void *)kvm_null_fn)

/* Iterate over each memslot intersecting [start, last] (inclusive) range */
#define kvm_for_each_memslot_in_hva_range(node, slots, start, last)	     \
	for (node = interval_tree_iter_first(&slots->hva_tree, start, last); \
	     node;							     \
	     node = interval_tree_iter_next(node, start, last))	     \

static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
						  const struct kvm_hva_range *range)
{
	bool ret = false, locked = false;
	struct kvm_gfn_range gfn_range;
	struct kvm_memory_slot *slot;
	struct kvm_memslots *slots;
	int i, idx;

	if (WARN_ON_ONCE(range->end <= range->start))
		return 0;

	/* A null handler is allowed if and only if on_lock() is provided. */
	if (WARN_ON_ONCE(IS_KVM_NULL_FN(range->on_lock) &&
			 IS_KVM_NULL_FN(range->handler)))
		return 0;

	idx = srcu_read_lock(&kvm->srcu);

	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
		struct interval_tree_node *node;

		slots = __kvm_memslots(kvm, i);
		kvm_for_each_memslot_in_hva_range(node, slots,
						  range->start, range->end - 1) {
			unsigned long hva_start, hva_end;

			slot = container_of(node, struct kvm_memory_slot, hva_node[slots->node_idx]);
			hva_start = max(range->start, slot->userspace_addr);
			hva_end = min(range->end, slot->userspace_addr +
						  (slot->npages << PAGE_SHIFT));

			/*
			 * To optimize for the likely case where the address
			 * range is covered by zero or one memslots, don't
			 * bother making these conditional (to avoid writes on
			 * the second or later invocation of the handler).
			 */
			gfn_range.pte = range->pte;
			gfn_range.may_block = range->may_block;

			/*
			 * {gfn(page) | page intersects with [hva_start, hva_end)} =
			 * {gfn_start, gfn_start+1, ..., gfn_end-1}.
			 */
			gfn_range.start = hva_to_gfn_memslot(hva_start, slot);
			gfn_range.end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, slot);
			gfn_range.slot = slot;

			if (!locked) {
				locked = true;
				KVM_MMU_LOCK(kvm);
				if (!IS_KVM_NULL_FN(range->on_lock))
					range->on_lock(kvm, range->start, range->end);
				if (IS_KVM_NULL_FN(range->handler))
					break;
			}
			ret |= range->handler(kvm, &gfn_range);
		}
	}

	if (range->flush_on_ret && ret)
		kvm_flush_remote_tlbs(kvm);

	if (locked) {
		KVM_MMU_UNLOCK(kvm);
		if (!IS_KVM_NULL_FN(range->on_unlock))
			range->on_unlock(kvm);
	}

	srcu_read_unlock(&kvm->srcu, idx);

	/* The notifiers are averse to booleans. :-( */
	return (int)ret;
}

static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
						unsigned long start,
						unsigned long end,
						pte_t pte,
						hva_handler_t handler)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);
	const struct kvm_hva_range range = {
		.start		= start,
		.end		= end,
		.pte		= pte,
		.handler	= handler,
		.on_lock	= (void *)kvm_null_fn,
		.on_unlock	= (void *)kvm_null_fn,
		.flush_on_ret	= true,
		.may_block	= false,
	};

	return __kvm_handle_hva_range(kvm, &range);
}

static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn,
							 unsigned long start,
							 unsigned long end,
							 hva_handler_t handler)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);
	const struct kvm_hva_range range = {
		.start		= start,
		.end		= end,
		.pte		= __pte(0),
		.handler	= handler,
		.on_lock	= (void *)kvm_null_fn,
		.on_unlock	= (void *)kvm_null_fn,
		.flush_on_ret	= false,
		.may_block	= false,
	};

	return __kvm_handle_hva_range(kvm, &range);
}
static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
					struct mm_struct *mm,
					unsigned long address,
					pte_t pte)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);

	trace_kvm_set_spte_hva(address);

	/*
	 * .change_pte() must be surrounded by .invalidate_range_{start,end}().
	 * If mmu_notifier_count is zero, then no in-progress invalidations,
	 * including this one, found a relevant memslot at start(); rechecking
	 * memslots here is unnecessary.  Note, a false positive (count elevated
	 * by a different invalidation) is sub-optimal but functionally ok.
	 */
	WARN_ON_ONCE(!READ_ONCE(kvm->mn_active_invalidate_count));
	if (!READ_ONCE(kvm->mmu_notifier_count))
		return;

	kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn);
}

void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,
				   unsigned long end)
{
	/*
	 * The count increase must become visible at unlock time as no
	 * spte can be established without taking the mmu_lock and
	 * count is also read inside the mmu_lock critical section.
	 */
	kvm->mmu_notifier_count++;
	if (likely(kvm->mmu_notifier_count == 1)) {
		kvm->mmu_notifier_range_start = start;
		kvm->mmu_notifier_range_end = end;
	} else {
		/*
		 * Fully tracking multiple concurrent ranges has diminishing
		 * returns. Keep things simple and just find the minimal range
		 * which includes the current and new ranges. As there won't be
		 * enough information to subtract a range after its invalidate
		 * completes, any ranges invalidated concurrently will
		 * accumulate and persist until all outstanding invalidates
		 * complete.
		 */
		kvm->mmu_notifier_range_start =
			min(kvm->mmu_notifier_range_start, start);
		kvm->mmu_notifier_range_end =
			max(kvm->mmu_notifier_range_end, end);
	}
}

static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
					const struct mmu_notifier_range *range)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);
	const struct kvm_hva_range hva_range = {
		.start		= range->start,
		.end		= range->end,
		.pte		= __pte(0),
		.handler	= kvm_unmap_gfn_range,
		.on_lock	= kvm_inc_notifier_count,
		.on_unlock	= kvm_arch_guest_memory_reclaimed,
		.flush_on_ret	= true,
		.may_block	= mmu_notifier_range_blockable(range),
	};

	trace_kvm_unmap_hva_range(range->start, range->end);

	/*
	 * Prevent memslot modification between range_start() and range_end()
	 * so that conditionally locking provides the same result in both
	 * functions.  Without that guarantee, the mmu_notifier_count
	 * adjustments will be imbalanced.
	 *
	 * Pairs with the decrement in range_end().
	 */
	spin_lock(&kvm->mn_invalidate_lock);
	kvm->mn_active_invalidate_count++;
	spin_unlock(&kvm->mn_invalidate_lock);

	gfn_to_pfn_cache_invalidate_start(kvm, range->start, range->end,
					  hva_range.may_block);

	__kvm_handle_hva_range(kvm, &hva_range);

	return 0;
}

void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,
				   unsigned long end)
{
	/*
	 * This sequence increase will notify the kvm page fault that
	 * the page that is going to be mapped in the spte could have
	 * been freed.
	 */
	kvm->mmu_notifier_seq++;
	smp_wmb();
	/*
	 * The above sequence increase must be visible before the
	 * below count decrease, which is ensured by the smp_wmb above
	 * in conjunction with the smp_rmb in mmu_notifier_retry().
	 */
	kvm->mmu_notifier_count--;
}

static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
					const struct mmu_notifier_range *range)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);
	const struct kvm_hva_range hva_range = {
		.start		= range->start,
		.end		= range->end,
		.pte		= __pte(0),
		.handler	= (void *)kvm_null_fn,
		.on_lock	= kvm_dec_notifier_count,
		.on_unlock	= (void *)kvm_null_fn,
		.flush_on_ret	= false,
		.may_block	= mmu_notifier_range_blockable(range),
	};
	bool wake;

	__kvm_handle_hva_range(kvm, &hva_range);

	/* Pairs with the increment in range_start(). */
	spin_lock(&kvm->mn_invalidate_lock);
	wake = (--kvm->mn_active_invalidate_count == 0);
	spin_unlock(&kvm->mn_invalidate_lock);

	/*
	 * There can only be one waiter, since the wait happens under
	 * slots_lock.
	 */
	if (wake)
		rcuwait_wake_up(&kvm->mn_memslots_update_rcuwait);

	BUG_ON(kvm->mmu_notifier_count < 0);
}

static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
					      struct mm_struct *mm,
					      unsigned long start,
					      unsigned long end)
{
	trace_kvm_age_hva(start, end);

	return kvm_handle_hva_range(mn, start, end, __pte(0), kvm_age_gfn);
}

static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
					struct mm_struct *mm,
					unsigned long start,
					unsigned long end)
{
	trace_kvm_age_hva(start, end);

	/*
	 * Even though we do not flush TLB, this will still adversely
	 * affect performance on pre-Haswell Intel EPT, where there is
	 * no EPT Access Bit to clear so that we have to tear down EPT
	 * tables instead. If we find this unacceptable, we can always
	 * add a parameter to kvm_age_hva so that it effectively doesn't
	 * do anything on clear_young.
	 *
	 * Also note that currently we never issue secondary TLB flushes
	 * from clear_young, leaving this job up to the regular system
	 * cadence. If we find this inaccurate, we might come up with a
	 * more sophisticated heuristic later.
	 */
	return kvm_handle_hva_range_no_flush(mn, start, end, kvm_age_gfn);
}

static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
				       struct mm_struct *mm,
				       unsigned long address)
{
	trace_kvm_test_age_hva(address);

	return kvm_handle_hva_range_no_flush(mn, address, address + 1,
					     kvm_test_age_gfn);
}

static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
				     struct mm_struct *mm)
{
	struct kvm *kvm = mmu_notifier_to_kvm(mn);
	int idx;

	idx = srcu_read_lock(&kvm->srcu);
	kvm_flush_shadow_all(kvm);
	srcu_read_unlock(&kvm->srcu, idx);
}

static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
	.invalidate_range	= kvm_mmu_notifier_invalidate_range,
	.invalidate_range_start	= kvm_mmu_notifier_invalidate_range_start,
	.invalidate_range_end	= kvm_mmu_notifier_invalidate_range_end,
	.clear_flush_young	= kvm_mmu_notifier_clear_flush_young,
	.clear_young		= kvm_mmu_notifier_clear_young,
	.test_young		= kvm_mmu_notifier_test_young,
	.change_pte		= kvm_mmu_notifier_change_pte,
	.release		= kvm_mmu_notifier_release,
};

static int kvm_init_mmu_notifier(struct kvm *kvm)
{
	kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
	return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
}

#else  /* !(CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER) */

static int kvm_init_mmu_notifier(struct kvm *kvm)
{
	return 0;
}

#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */

#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
static int kvm_pm_notifier_call(struct notifier_block *bl,
				unsigned long state,
				void *unused)
{
	struct kvm *kvm = container_of(bl, struct kvm, pm_notifier);

	return kvm_arch_pm_notifier(kvm, state);
}

static void kvm_init_pm_notifier(struct kvm *kvm)
{
	kvm->pm_notifier.notifier_call = kvm_pm_notifier_call;
	/* Suspend KVM before we suspend ftrace, RCU, etc. */
	kvm->pm_notifier.priority = INT_MAX;
	register_pm_notifier(&kvm->pm_notifier);
}

static void kvm_destroy_pm_notifier(struct kvm *kvm)
{
	unregister_pm_notifier(&kvm->pm_notifier);
}
#else /* !CONFIG_HAVE_KVM_PM_NOTIFIER */
static void kvm_init_pm_notifier(struct kvm *kvm)
{
}

static void kvm_destroy_pm_notifier(struct kvm *kvm)
{
}
#endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */

static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
{
	if (!memslot->dirty_bitmap)
		return;

	kvfree(memslot->dirty_bitmap);
	memslot->dirty_bitmap = NULL;
}

/* This does not remove the slot from struct kvm_memslots data structures */
static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
{
	kvm_destroy_dirty_bitmap(slot);

	kvm_arch_free_memslot(kvm, slot);

	kfree(slot);
}

static void kvm_free_memslots(struct kvm *kvm, struct kvm_memslots *slots)
{
	struct hlist_node *idnode;
	struct kvm_memory_slot *memslot;
	int bkt;

	/*
	 * The same memslot objects live in both active and inactive sets,
	 * arbitrarily free using index '1' so the second invocation of this
	 * function isn't operating over a structure with dangling pointers
	 * (even though this function isn't actually touching them).
	 */
	if (!slots->node_idx)
		return;

	hash_for_each_safe(slots->id_hash, bkt, idnode, memslot, id_node[1])
		kvm_free_memslot(kvm, memslot);
}

static umode_t kvm_stats_debugfs_mode(const struct _kvm_stats_desc *pdesc)
{
	switch (pdesc->desc.flags & KVM_STATS_TYPE_MASK) {
	case KVM_STATS_TYPE_INSTANT:
		return 0444;
	case KVM_STATS_TYPE_CUMULATIVE:
	case KVM_STATS_TYPE_PEAK:
	default:
		return 0644;
	}
}


static void kvm_destroy_vm_debugfs(struct kvm *kvm)
{
	int i;
	int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc +
				      kvm_vcpu_stats_header.num_desc;

	if (IS_ERR(kvm->debugfs_dentry))
		return;

	debugfs_remove_recursive(kvm->debugfs_dentry);

	if (kvm->debugfs_stat_data) {
		for (i = 0; i < kvm_debugfs_num_entries; i++)
			kfree(kvm->debugfs_stat_data[i]);
		kfree(kvm->debugfs_stat_data);
	}
}

static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
{
	static DEFINE_MUTEX(kvm_debugfs_lock);
	struct dentry *dent;
	char dir_name[ITOA_MAX_LEN * 2];
	struct kvm_stat_data *stat_data;
	const struct _kvm_stats_desc *pdesc;
	int i, ret;
	int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc +
				      kvm_vcpu_stats_header.num_desc;

	if (!debugfs_initialized())
		return 0;

	snprintf(dir_name, sizeof(dir_name), "%d-%d", task_pid_nr(current), fd);
	mutex_lock(&kvm_debugfs_lock);
	dent = debugfs_lookup(dir_name, kvm_debugfs_dir);
	if (dent) {
		pr_warn_ratelimited("KVM: debugfs: duplicate directory %s\n", dir_name);
		dput(dent);
		mutex_unlock(&kvm_debugfs_lock);
		return 0;
	}
	dent = debugfs_create_dir(dir_name, kvm_debugfs_dir);
	mutex_unlock(&kvm_debugfs_lock);
	if (IS_ERR(dent))
		return 0;

	kvm->debugfs_dentry = dent;
	kvm->debugfs_stat_data = kcalloc(kvm_debugfs_num_entries,
					 sizeof(*kvm->debugfs_stat_data),
					 GFP_KERNEL_ACCOUNT);
	if (!kvm->debugfs_stat_data)
		return -ENOMEM;

	for (i = 0; i < kvm_vm_stats_header.num_desc; ++i) {
		pdesc = &kvm_vm_stats_desc[i];
		stat_data = kzalloc(sizeof(*stat_data), GFP_KERNEL_ACCOUNT);
		if (!stat_data)
			return -ENOMEM;

		stat_data->kvm = kvm;
		stat_data->desc = pdesc;
		stat_data->kind = KVM_STAT_VM;
		kvm->debugfs_stat_data[i] = stat_data;
		debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
				    kvm->debugfs_dentry, stat_data,
				    &stat_fops_per_vm);
	}

	for (i = 0; i < kvm_vcpu_stats_header.num_desc; ++i) {
		pdesc = &kvm_vcpu_stats_desc[i];
		stat_data = kzalloc(sizeof(*stat_data), GFP_KERNEL_ACCOUNT);
		if (!stat_data)
			return -ENOMEM;

		stat_data->kvm = kvm;
		stat_data->desc = pdesc;
		stat_data->kind = KVM_STAT_VCPU;
		kvm->debugfs_stat_data[i + kvm_vm_stats_header.num_desc] = stat_data;
		debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
				    kvm->debugfs_dentry, stat_data,
				    &stat_fops_per_vm);
	}

	ret = kvm_arch_create_vm_debugfs(kvm);
	if (ret) {
		kvm_destroy_vm_debugfs(kvm);
		return i;
	}

	return 0;
}

/*
 * Called after the VM is otherwise initialized, but just before adding it to
 * the vm_list.
 */
int __weak kvm_arch_post_init_vm(struct kvm *kvm)
{
	return 0;
}

/*
 * Called just after removing the VM from the vm_list, but before doing any
 * other destruction.
 */
void __weak kvm_arch_pre_destroy_vm(struct kvm *kvm)
{
}

/*
 * Called after per-vm debugfs created.  When called kvm->debugfs_dentry should
 * be setup already, so we can create arch-specific debugfs entries under it.
 * Cleanup should be automatic done in kvm_destroy_vm_debugfs() recursively, so
 * a per-arch destroy interface is not needed.
 */
int __weak kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
	return 0;
}

static struct kvm *kvm_create_vm(unsigned long type)
{
	struct kvm *kvm = kvm_arch_alloc_vm();
	struct kvm_memslots *slots;
	int r = -ENOMEM;
	int i, j;

	if (!kvm)
		return ERR_PTR(-ENOMEM);

	KVM_MMU_LOCK_INIT(kvm);
	mmgrab(current->mm);
	kvm->mm = current->mm;
	kvm_eventfd_init(kvm);
	mutex_init(&kvm->lock);
	mutex_init(&kvm->irq_lock);
	mutex_init(&kvm->slots_lock);
	mutex_init(&kvm->slots_arch_lock);
	spin_lock_init(&kvm->mn_invalidate_lock);
	rcuwait_init(&kvm->mn_memslots_update_rcuwait);
	xa_init(&kvm->vcpu_array);

	INIT_LIST_HEAD(&kvm->gpc_list);
	spin_lock_init(&kvm->gpc_lock);

	INIT_LIST_HEAD(&kvm->devices);
	kvm->max_vcpus = KVM_MAX_VCPUS;

	BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX);

	/*
	 * Force subsequent debugfs file creations to fail if the VM directory
	 * is not created (by kvm_create_vm_debugfs()).
	 */
	kvm->debugfs_dentry = ERR_PTR(-ENOENT);

	if (init_srcu_struct(&kvm->srcu))
		goto out_err_no_srcu;
	if (init_srcu_struct(&kvm->irq_srcu))
		goto out_err_no_irq_srcu;

	refcount_set(&kvm->users_count, 1);
	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
		for (j = 0; j < 2; j++) {
			slots = &kvm->__memslots[i][j];

			atomic_long_set(&slots->last_used_slot, (unsigned long)NULL);
			slots->hva_tree = RB_ROOT_CACHED;
			slots->gfn_tree = RB_ROOT;
			hash_init(slots->id_hash);
			slots->node_idx = j;

			/* Generations must be different for each address space. */
			slots->generation = i;
		}

		rcu_assign_pointer(kvm->memslots[i], &kvm->__memslots[i][0]);
	}

	for (i = 0; i < KVM_NR_BUSES; i++) {
		rcu_assign_pointer(kvm->buses[i],
			kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL_ACCOUNT));
		if (!kvm->buses[i])
			goto out_err_no_arch_destroy_vm;
	}

	kvm->max_halt_poll_ns = halt_poll_ns;

	r = kvm_arch_init_vm(kvm, type);
	if (r)
		goto out_err_no_arch_destroy_vm;

	r = hardware_enable_all();
	if (r)
		goto out_err_no_disable;

#ifdef CONFIG_HAVE_KVM_IRQFD
	INIT_HLIST_HEAD(&kvm->irq_ack_notifier_list);
#endif

	r = kvm_init_mmu_notifier(kvm);
	if (r)
		goto out_err_no_mmu_notifier;

	r = kvm_arch_post_init_vm(kvm);
	if (r)
		goto out_err;

	mutex_lock(&kvm_lock);
	list_add(&kvm->vm_list, &vm_list);
	mutex_unlock(&kvm_lock);

	preempt_notifier_inc();
	kvm_init_pm_notifier(kvm);

	/*
	 * When the fd passed to this ioctl() is opened it pins the module,
	 * but try_module_get() also prevents getting a reference if the module
	 * is in MODULE_STATE_GOING (e.g. if someone ran "rmmod --wait").
	 */
	if (!try_module_get(kvm_chardev_ops.owner)) {
		r = -ENODEV;
		goto out_err;
	}

	return kvm;

out_err:
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
	if (kvm->mmu_notifier.ops)
		mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
#endif
out_err_no_mmu_notifier:
	hardware_disable_all();
out_err_no_disable:
	kvm_arch_destroy_vm(kvm);
out_err_no_arch_destroy_vm:
	WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count));
	for (i = 0; i < KVM_NR_BUSES; i++)
		kfree(kvm_get_bus(kvm, i));
	cleanup_srcu_struct(&kvm->irq_srcu);
out_err_no_irq_srcu:
	cleanup_srcu_struct(&kvm->srcu);
out_err_no_srcu:
	kvm_arch_free_vm(kvm);
	mmdrop(current->mm);
	return ERR_PTR(r);
}

static void kvm_destroy_devices(struct kvm *kvm)
{
	struct kvm_device *dev, *tmp;

	/*
	 * We do not need to take the kvm->lock here, because nobody else
	 * has a reference to the struct kvm at this point and therefore
	 * cannot access the devices list anyhow.
	 */
	list_for_each_entry_safe(dev, tmp, &kvm->devices, vm_node) {
		list_del(&dev->vm_node);
		dev->ops->destroy(dev);
	}
}

static void kvm_destroy_vm(struct kvm *kvm)
{
	int i;
	struct mm_struct *mm = kvm->mm;

	kvm_destroy_pm_notifier(kvm);
	kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm);
	kvm_destroy_vm_debugfs(kvm);
	kvm_arch_sync_events(kvm);
	mutex_lock(&kvm_lock);
	list_del(&kvm->vm_list);
	mutex_unlock(&kvm_lock);
	kvm_arch_pre_destroy_vm(kvm);

	kvm_free_irq_routing(kvm);
	for (i = 0; i < KVM_NR_BUSES; i++) {
		struct kvm_io_bus *bus = kvm_get_bus(kvm, i);

		if (bus)
			kvm_io_bus_destroy(bus);
		kvm->buses[i] = NULL;
	}
	kvm_coalesced_mmio_free(kvm);
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
	mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
	/*
	 * At this point, pending calls to invalidate_range_start()
	 * have completed but no more MMU notifiers will run, so
	 * mn_active_invalidate_count may remain unbalanced.
	 * No threads can be waiting in install_new_memslots as the
	 * last reference on KVM has been dropped, but freeing
	 * memslots would deadlock without this manual intervention.
	 */
	WARN_ON(rcuwait_active(&kvm->mn_memslots_update_rcuwait));
	kvm->mn_active_invalidate_count = 0;
#else
	kvm_flush_shadow_all(kvm);
#endif
	kvm_arch_destroy_vm(kvm);
	kvm_destroy_devices(kvm);
	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
		kvm_free_memslots(kvm, &kvm->__memslots[i][0]);
		kvm_free_memslots(kvm, &kvm->__memslots[i][1]);
	}
	cleanup_srcu_struct(&kvm->irq_srcu);
	cleanup_srcu_struct(&kvm->srcu);
	kvm_arch_free_vm(kvm);
	preempt_notifier_dec();
	hardware_disable_all();
	mmdrop(mm);
	module_put(kvm_chardev_ops.owner);
}

void kvm_get_kvm(struct kvm *kvm)
{
	refcount_inc(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm);

/*
 * Make sure the vm is not during destruction, which is a safe version of
 * kvm_get_kvm().  Return true if kvm referenced successfully, false otherwise.
 */
bool kvm_get_kvm_safe(struct kvm *kvm)
{
	return refcount_inc_not_zero(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm_safe);

void kvm_put_kvm(struct kvm *kvm)
{
	if (refcount_dec_and_test(&kvm->users_count))
		kvm_destroy_vm(kvm);
}
EXPORT_SYMBOL_GPL(kvm_put_kvm);

/*
 * Used to put a reference that was taken on behalf of an object associated
 * with a user-visible file descriptor, e.g. a vcpu or device, if installation
 * of the new file descriptor fails and the reference cannot be transferred to
 * its final owner.  In such cases, the caller is still actively using @kvm and
 * will fail miserably if the refcount unexpectedly hits zero.
 */
void kvm_put_kvm_no_destroy(struct kvm *kvm)
{
	WARN_ON(refcount_dec_and_test(&kvm->users_count));
}
EXPORT_SYMBOL_GPL(kvm_put_kvm_no_destroy);

static int kvm_vm_release(struct inode *inode, struct file *filp)
{
	struct kvm *kvm = filp->private_data;

	kvm_irqfd_release(kvm);

	kvm_put_kvm(kvm);
	return 0;
}

/*
 * Allocation size is twice as large as the actual dirty bitmap size.
 * See kvm_vm_ioctl_get_dirty_log() why this is needed.
 */
static int kvm_alloc_dirty_bitmap(struct kvm_memory_slot *memslot)
{
	unsigned long dirty_bytes = kvm_dirty_bitmap_bytes(memslot);

	memslot->dirty_bitmap = __vcalloc(2, dirty_bytes, GFP_KERNEL_ACCOUNT);
	if (!memslot->dirty_bitmap)
		return -ENOMEM;

	return 0;
}

static struct kvm_memslots *kvm_get_inactive_memslots(struct kvm *kvm, int as_id)
{
	struct kvm_memslots *active = __kvm_memslots(kvm, as_id);
	int node_idx_inactive = active->node_idx ^ 1;

	return &kvm->__memslots[as_id][node_idx_inactive];
}

/*
 * Helper to get the address space ID when one of memslot pointers may be NULL.
 * This also serves as a sanity that at least one of the pointers is non-NULL,
 * and that their address space IDs don't diverge.
 */
static int kvm_memslots_get_as_id(struct kvm_memory_slot *a,
				  struct kvm_memory_slot *b)
{
	if (WARN_ON_ONCE(!a && !b))
		return 0;

	if (!a)
		return b->as_id;
	if (!b)
		return a->as_id;

	WARN_ON_ONCE(a->as_id != b->as_id);
	return a->as_id;
}

static void kvm_insert_gfn_node(struct kvm_memslots *slots,
				struct kvm_memory_slot *slot)
{
	struct rb_root *gfn_tree = &slots->gfn_tree;
	struct rb_node **node, *parent;
	int idx = slots->node_idx;

	parent = NULL;
	for (node = &gfn_tree->rb_node; *node; ) {
		struct kvm_memory_slot *tmp;

		tmp = container_of(*node, struct kvm_memory_slot, gfn_node[idx]);
		parent = *node;
		if (slot->base_gfn < tmp->base_gfn)
			node = &(*node)->rb_left;
		else if (slot->base_gfn > tmp->base_gfn)
			node = &(*node)->rb_right;
		else
			BUG();
	}

	rb_link_node(&slot->gfn_node[idx], parent, node);
	rb_insert_color(&slot->gfn_node[idx], gfn_tree);
}

static void kvm_erase_gfn_node(struct kvm_memslots *slots,
			       struct kvm_memory_slot *slot)
{
	rb_erase(&slot->gfn_node[slots->node_idx], &slots->gfn_tree);
}

static void kvm_replace_gfn_node(struct kvm_memslots *slots,
				 struct kvm_memory_slot *old,
				 struct kvm_memory_slot *new)
{
	int idx = slots->node_idx;

	WARN_ON_ONCE(old->base_gfn != new->base_gfn);

	rb_replace_node(&old->gfn_node[idx], &new->gfn_node[idx],
			&slots->gfn_tree);
}

/*
 * Replace @old with @new in the inactive memslots.
 *
 * With NULL @old this simply adds @new.
 * With NULL @new this simply removes @old.
 *
 * If @new is non-NULL its hva_node[slots_idx] range has to be set
 * appropriately.
 */
static void kvm_replace_memslot(struct kvm *kvm,
				struct kvm_memory_slot *old,
				struct kvm_memory_slot *new)
{
	int as_id = kvm_memslots_get_as_id(old, new);
	struct kvm_memslots *slots = kvm_get_inactive_memslots(kvm, as_id);
	int idx = slots->node_idx;

	if (old) {
		hash_del(&old->id_node[idx]);
		interval_tree_remove(&old->hva_node[idx], &slots->hva_tree);

		if ((long)old == atomic_long_read(&slots->last_used_slot))
			atomic_long_set(&slots->last_used_slot, (long)new);

		if (!new) {
			kvm_erase_gfn_node(slots, old);
			return;
		}
	}

	/*
	 * Initialize @new's hva range.  Do this even when replacing an @old
	 * slot, kvm_copy_memslot() deliberately does not touch node data.
	 */
	new->hva_node[idx].start = new->userspace_addr;
	new->hva_node[idx].last = new->userspace_addr +
				  (new->npages << PAGE_SHIFT) - 1;

	/*
	 * (Re)Add the new memslot.  There is no O(1) interval_tree_replace(),
	 * hva_node needs to be swapped with remove+insert even though hva can't
	 * change when replacing an existing slot.
	 */
	hash_add(slots->id_hash, &new->id_node[idx], new->id);
	interval_tree_insert(&new->hva_node[idx], &slots->hva_tree);

	/*
	 * If the memslot gfn is unchanged, rb_replace_node() can be used to
	 * switch the node in the gfn tree instead of removing the old and
	 * inserting the new as two separate operations. Replacement is a
	 * single O(1) operation versus two O(log(n)) operations for
	 * remove+insert.
	 */
	if (old && old->base_gfn == new->base_gfn) {
		kvm_replace_gfn_node(slots, old, new);
	} else {
		if (old)
			kvm_erase_gfn_node(slots, old);
		kvm_insert_gfn_node(slots, new);
	}
}

static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
{
	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;

#ifdef __KVM_HAVE_READONLY_MEM
	valid_flags |= KVM_MEM_READONLY;
#endif

	if (mem->flags & ~valid_flags)
		return -EINVAL;

	return 0;
}

static void kvm_swap_active_memslots(struct kvm *kvm, int as_id)
{
	struct kvm_memslots *slots = kvm_get_inactive_memslots(kvm, as_id);

	/* Grab the generation from the activate memslots. */
	u64 gen = __kvm_memslots(kvm, as_id)->generation;

	WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
	slots->generation = gen | KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;

	/*
	 * Do not store the new memslots while there are invalidations in
	 * progress, otherwise the locking in invalidate_range_start and
	 * invalidate_range_end will be unbalanced.
	 */
	spin_lock(&kvm->mn_invalidate_lock);
	prepare_to_rcuwait(&kvm->mn_memslots_update_rcuwait);
	while (kvm->mn_active_invalidate_count) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		spin_unlock(&kvm->mn_invalidate_lock);
		schedule();
		spin_lock(&kvm->mn_invalidate_lock);
	}
	finish_rcuwait(&kvm->mn_memslots_update_rcuwait);
	rcu_assign_pointer(kvm->memslots[as_id], slots);
	spin_unlock(&kvm->mn_invalidate_lock);

	/*
	 * Acquired in kvm_set_memslot. Must be released before synchronize
	 * SRCU below in order to avoid deadlock with another thread
	 * acquiring the slots_arch_lock in an srcu critical section.
	 */
	mutex_unlock(&kvm->slots_arch_lock);

	synchronize_srcu_expedited(&kvm->srcu);

	/*
	 * Increment the new memslot generation a second time, dropping the
	 * update in-progress flag and incrementing the generation based on
	 * the number of address spaces.  This provides a unique and easily
	 * identifiable generation number while the memslots are in flux.
	 */
	gen = slots->generation & ~KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;

	/*
	 * Generations must be unique even across address spaces.  We do not need
	 * a global counter for that, instead the generation space is evenly split
	 * across address spaces.  For example, with two address spaces, address
	 * space 0 will use generations 0, 2, 4, ... while address space 1 will
	 * use generations 1, 3, 5, ...
	 */
	gen += KVM_ADDRESS_SPACE_NUM;

	kvm_arch_memslots_updated(kvm, gen);

	slots->generation = gen;
}

static int kvm_prepare_memory_region(struct kvm *kvm,
				     const struct kvm_memory_slot *old,
				     struct kvm_memory_slot *new,
				     enum kvm_mr_change change)
{
	int r;

	/*
	 * If dirty logging is disabled, nullify the bitmap; the old bitmap
	 * will be freed on "commit".  If logging is enabled in both old and
	 * new, reuse the existing bitmap.  If logging is enabled only in the
	 * new and KVM isn't using a ring buffer, allocate and initialize a
	 * new bitmap.
	 */
	if (change != KVM_MR_DELETE) {
		if (!(new->flags & KVM_MEM_LOG_DIRTY_PAGES))
			new->dirty_bitmap = NULL;
		else if (old && old->dirty_bitmap)
			new->dirty_bitmap = old->dirty_bitmap;
		else if (!kvm->dirty_ring_size) {
			r = kvm_alloc_dirty_bitmap(new);
			if (r)
				return r;

			if (kvm_dirty_log_manual_protect_and_init_set(kvm))
				bitmap_set(new->dirty_bitmap, 0, new->npages);
		}
	}

	r = kvm_arch_prepare_memory_region(kvm, old, new, change);

	/* Free the bitmap on failure if it was allocated above. */
	if (r && new && new->dirty_bitmap && old && !old->dirty_bitmap)
		kvm_destroy_dirty_bitmap(new);

	return r;
}

static void kvm_commit_memory_region(struct kvm *kvm,
				     struct kvm_memory_slot *old,
				     const struct kvm_memory_slot *new,
				     enum kvm_mr_change change)
{
	/*
	 * Update the total number of memslot pages before calling the arch
	 * hook so that architectures can consume the result directly.
	 */
	if (change == KVM_MR_DELETE)
		kvm->nr_memslot_pages -= old->npages;
	else if (change == KVM_MR_CREATE)
		kvm->nr_memslot_pages += new->npages;

	kvm_arch_commit_memory_region(kvm, old, new, change);

	switch (change) {
	case KVM_MR_CREATE:
		/* Nothing more to do. */
		break;
	case KVM_MR_DELETE:
		/* Free the old memslot and all its metadata. */
		kvm_free_memslot(kvm, old);
		break;
	case KVM_MR_MOVE:
	case KVM_MR_FLAGS_ONLY:
		/*
		 * Free the dirty bitmap as needed; the below check encompasses
		 * both the flags and whether a ring buffer is being used)
		 */
		if (old->dirty_bitmap && !new->dirty_bitmap)
			kvm_destroy_dirty_bitmap(old);

		/*
		 * The final quirk.  Free the detached, old slot, but only its
		 * memory, not any metadata.  Metadata, including arch specific
		 * data, may be reused by @new.
		 */
		kfree(old);
		break;
	default:
		BUG();
	}
}

/*
 * Activate @new, which must be installed in the inactive slots by the caller,
 * by swapping the active slots and then propagating @new to @old once @old is
 * unreachable and can be safely modified.
 *
 * With NULL @old this simply adds @new to @active (while swapping the sets).
 * With NULL @new this simply removes @old from @active and frees it
 * (while also swapping the sets).
 */
static void kvm_activate_memslot(struct kvm *kvm,
				 struct kvm_memory_slot *old,
				 struct kvm_memory_slot *new)
{
	int as_id = kvm_memslots_get_as_id(old, new);

	kvm_swap_active_memslots(kvm, as_id);

	/* Propagate the new memslot to the now inactive memslots. */
	kvm_replace_memslot(kvm, old, new);
}

static void kvm_copy_memslot(struct kvm_memory_slot *dest,
			     const struct kvm_memory_slot *src)
{
	dest->base_gfn = src->base_gfn;
	dest->npages = src->npages;
	dest->dirty_bitmap = src->dirty_bitmap;
	dest->arch = src->arch;
	dest->userspace_addr = src->userspace_addr;
	dest->flags = src->flags;
	dest->id = src->id;
	dest->as_id = src->as_id;
}

static void kvm_invalidate_memslot(struct kvm *kvm,
				   struct kvm_memory_slot *old,
				   struct kvm_memory_slot *invalid_slot)
{
	/*
	 * Mark the current slot INVALID.  As with all memslot modifications,
	 * this must be done on an unreachable slot to avoid modifying the
	 * current slot in the active tree.
	 */
	kvm_copy_memslot(invalid_slot, old);
	invalid_slot->flags |= KVM_MEMSLOT_INVALID;
	kvm_replace_memslot(kvm, old, invalid_slot);

	/*
	 * Activate the slot that is now marked INVALID, but don't propagate
	 * the slot to the now inactive slots. The slot is either going to be
	 * deleted or recreated as a new slot.
	 */
	kvm_swap_active_memslots(kvm, old->as_id);

	/*
	 * From this point no new shadow pages pointing to a deleted, or moved,
	 * memslot will be created.  Validation of sp->gfn happens in:
	 *	- gfn_to_hva (kvm_read_guest, gfn_to_pfn)
	 *	- kvm_is_visible_gfn (mmu_check_root)
	 */
	kvm_arch_flush_shadow_memslot(kvm, old);
	kvm_arch_guest_memory_reclaimed(kvm);

	/* Was released by kvm_swap_active_memslots, reacquire. */
	mutex_lock(&kvm->slots_arch_lock);

	/*
	 * Copy the arch-specific field of the newly-installed slot back to the
	 * old slot as the arch data could have changed between releasing
	 * slots_arch_lock in install_new_memslots() and re-acquiring the lock
	 * above.  Writers are required to retrieve memslots *after* acquiring
	 * slots_arch_lock, thus the active slot's data is guaranteed to be fresh.
	 */
	old->arch = invalid_slot->arch;
}

static void kvm_create_memslot(struct kvm *kvm,
			       struct kvm_memory_slot *new)
{
	/* Add the new memslot to the inactive set and activate. */
	kvm_replace_memslot(kvm, NULL, new);
	kvm_activate_memslot(kvm, NULL, new);
}

static void kvm_delete_memslot(struct kvm *kvm,
			       struct kvm_memory_slot *old,
			       struct kvm_memory_slot *invalid_slot)
{
	/*
	 * Remove the old memslot (in the inactive memslots) by passing NULL as
	 * the "new" slot, and for the invalid version in the active slots.
	 */
	kvm_replace_memslot(kvm, old, NULL);
	kvm_activate_memslot(kvm, invalid_slot, NULL);
}

static void kvm_move_memslot(struct kvm *kvm,
			     struct kvm_memory_slot *old,
			     struct kvm_memory_slot *new,
			     struct kvm_memory_slot *invalid_slot)
{
	/*
	 * Replace the old memslot in the inactive slots, and then swap slots
	 * and replace the current INVALID with the new as well.
	 */
	kvm_replace_memslot(kvm, old, new);
	kvm_activate_memslot(kvm, invalid_slot, new);
}

static void kvm_update_flags_memslot(struct kvm *kvm,
				     struct kvm_memory_slot *old,
				     struct kvm_memory_slot *new)
{
	/*
	 * Similar to the MOVE case, but the slot doesn't need to be zapped as
	 * an intermediate step. Instead, the old memslot is simply replaced
	 * with a new, updated copy in both memslot sets.
	 */
	kvm_replace_memslot(kvm, old, new);
	kvm_activate_memslot(kvm, old, new);
}

static int kvm_set_memslot(struct kvm *kvm,
			   struct kvm_memory_slot *old,
			   struct kvm_memory_slot *new,
			   enum kvm_mr_change change)
{
	struct kvm_memory_slot *invalid_slot;
	int r;

	/*
	 * Released in kvm_swap_active_memslots.
	 *
	 * Must be held from before the current memslots are copied until
	 * after the new memslots are installed with rcu_assign_pointer,
	 * then released before the synchronize srcu in kvm_swap_active_memslots.
	 *
	 * When modifying memslots outside of the slots_lock, must be held
	 * before reading the pointer to the current memslots until after all
	 * changes to those memslots are complete.
	 *
	 * These rules ensure that installing new memslots does not lose
	 * changes made to the previous memslots.
	 */
	mutex_lock(&kvm->slots_arch_lock);

	/*
	 * Invalidate the old slot if it's being deleted or moved.  This is
	 * done prior to actually deleting/moving the memslot to allow vCPUs to
	 * continue running by ensuring there are no mappings or shadow pages
	 * for the memslot when it is deleted/moved.  Without pre-invalidation
	 * (and without a lock), a window would exist between effecting the
	 * delete/move and committing the changes in arch code where KVM or a
	 * guest could access a non-existent memslot.
	 *
	 * Modifications are done on a temporary, unreachable slot.  The old
	 * slot needs to be preserved in case a later step fails and the
	 * invalidation needs to be reverted.
	 */
	if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
		invalid_slot = kzalloc(sizeof(*invalid_slot), GFP_KERNEL_ACCOUNT);
		if (!invalid_slot) {
			mutex_unlock(&kvm->slots_arch_lock);
			return -ENOMEM;
		}
		kvm_invalidate_memslot(kvm, old, invalid_slot);
	}

	r = kvm_prepare_memory_region(kvm, old, new, change);
	if (r) {
		/*
		 * For DELETE/MOVE, revert the above INVALID change.  No
		 * modifications required since the original slot was preserved
		 * in the inactive slots.  Changing the active memslots also
		 * release slots_arch_lock.
		 */
		if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
			kvm_activate_memslot(kvm, invalid_slot, old);
			kfree(invalid_slot);
		} else {
			mutex_unlock(&kvm->slots_arch_lock);
		}
		return r;
	}

	/*
	 * For DELETE and MOVE, the working slot is now active as the INVALID
	 * version of the old slot.  MOVE is particularly special as it reuses
	 * the old slot and returns a copy of the old slot (in working_slot).
	 * For CREATE, there is no old slot.  For DELETE and FLAGS_ONLY, the
	 * old slot is detached but otherwise preserved.
	 */
	if (change == KVM_MR_CREATE)
		kvm_create_memslot(kvm, new);
	else if (change == KVM_MR_DELETE)
		kvm_delete_memslot(kvm, old, invalid_slot);
	else if (change == KVM_MR_MOVE)
		kvm_move_memslot(kvm, old, new, invalid_slot);
	else if (change == KVM_MR_FLAGS_ONLY)
		kvm_update_flags_memslot(kvm, old, new);
	else
		BUG();

	/* Free the temporary INVALID slot used for DELETE and MOVE. */
	if (change == KVM_MR_DELETE || change == KVM_MR_MOVE)
		kfree(invalid_slot);

	/*
	 * No need to refresh new->arch, changes after dropping slots_arch_lock
	 * will directly hit the final, active memslot.  Architectures are
	 * responsible for knowing that new->arch may be stale.
	 */
	kvm_commit_memory_region(kvm, old, new, change);

	return 0;
}

static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
				      gfn_t start, gfn_t end)
{
	struct kvm_memslot_iter iter;

	kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
		if (iter.slot->id != id)
			return true;
	}

	return false;
}

/*
 * Allocate some memory and give it an address in the guest physical address
 * space.
 *
 * Discontiguous memory is allowed, mostly for framebuffers.
 *
 * Must be called holding kvm->slots_lock for write.
 */
int __kvm_set_memory_region(struct kvm *kvm,
			    const struct kvm_userspace_memory_region *mem)
{
	struct kvm_memory_slot *old, *new;
	struct kvm_memslots *slots;
	enum kvm_mr_change change;
	unsigned long npages;
	gfn_t base_gfn;
	int as_id, id;
	int r;

	r = check_memory_region_flags(mem);
	if (r)
		return r;

	as_id = mem->slot >> 16;
	id = (u16)mem->slot;

	/* General sanity checks */
	if ((mem->memory_size & (PAGE_SIZE - 1)) ||
	    (mem->memory_size != (unsigned long)mem->memory_size))
		return -EINVAL;
	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
		return -EINVAL;
	/* We can read the guest memory with __xxx_user() later on. */
	if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
	    (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
			mem->memory_size))
		return -EINVAL;
	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
		return -EINVAL;
	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
		return -EINVAL;
	if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
		return -EINVAL;

	slots = __kvm_memslots(kvm, as_id);

	/*
	 * Note, the old memslot (and the pointer itself!) may be invalidated
	 * and/or destroyed by kvm_set_memslot().
	 */
	old = id_to_memslot(slots, id);

	if (!mem->memory_size) {
		if (!old || !old->npages)
			return -EINVAL;

		if (WARN_ON_ONCE(kvm->nr_memslot_pages < old->npages))
			return -EIO;

		return kvm_set_memslot(kvm, old, NULL, KVM_MR_DELETE);
	}

	base_gfn = (mem->guest_phys_addr >> PAGE_SHIFT);
	npages = (mem->memory_size >> PAGE_SHIFT);

	if (!old || !old->npages) {
		change = KVM_MR_CREATE;

		/*
		 * To simplify KVM internals, the total number of pages across
		 * all memslots must fit in an unsigned long.
		 */
		if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages)
			return -EINVAL;
	} else { /* Modify an existing slot. */
		if ((mem->userspace_addr != old->userspace_addr) ||
		    (npages != old->npages) ||
		    ((mem->flags ^ old->flags) & KVM_MEM_READONLY))
			return -EINVAL;

		if (base_gfn != old->base_gfn)
			change = KVM_MR_MOVE;
		else if (mem->flags != old->flags)
			change = KVM_MR_FLAGS_ONLY;
		else /* Nothing to change. */
			return 0;
	}

	if ((change == KVM_MR_CREATE || change == KVM_MR_MOVE) &&
	    kvm_check_memslot_overlap(slots, id, base_gfn, base_gfn + npages))
		return -EEXIST;

	/* Allocate a slot that will persist in the memslot. */
	new = kzalloc(sizeof(*new), GFP_KERNEL_ACCOUNT);
	if (!new)
		return -ENOMEM;

	new->as_id = as_id;
	new->id = id;
	new->base_gfn = base_gfn;
	new->npages = npages;
	new->flags = mem->flags;
	new->userspace_addr = mem->userspace_addr;

	r = kvm_set_memslot(kvm, old, new, change);
	if (r)
		kfree(new);
	return r;
}
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);

int kvm_set_memory_region(struct kvm *kvm,
			  const struct kvm_userspace_memory_region *mem)
{
	int r;

	mutex_lock(&kvm->slots_lock);
	r = __kvm_set_memory_region(kvm, mem);
	mutex_unlock(&kvm->slots_lock);
	return r;
}
EXPORT_SYMBOL_GPL(kvm_set_memory_region);

static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
					  struct kvm_userspace_memory_region *mem)
{
	if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)
		return -EINVAL;

	return kvm_set_memory_region(kvm, mem);
}

#ifndef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
/**
 * kvm_get_dirty_log - get a snapshot of dirty pages
 * @kvm:	pointer to kvm instance
 * @log:	slot id and address to which we copy the log
 * @is_dirty:	set to '1' if any dirty pages were found
 * @memslot:	set to the associated memslot, always valid on success
 */
int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
		      int *is_dirty, struct kvm_memory_slot **memslot)
{
	struct kvm_memslots *slots;
	int i, as_id, id;
	unsigned long n;
	unsigned long any = 0;

	/* Dirty ring tracking is exclusive to dirty log tracking */
	if (kvm->dirty_ring_size)
		return -ENXIO;

	*memslot = NULL;
	*is_dirty = 0;

	as_id = log->slot >> 16;
	id = (u16)log->slot;
	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
		return -EINVAL;

	slots = __kvm_memslots(kvm, as_id);
	*memslot = id_to_memslot(slots, id);
	if (!(*memslot) || !(*memslot)->dirty_bitmap)
		return -ENOENT;

	kvm_arch_sync_dirty_log(kvm, *memslot);

	n = kvm_dirty_bitmap_bytes(*memslot);

	for (i = 0; !any && i < n/sizeof(long); ++i)
		any = (*memslot)->dirty_bitmap[i];

	if (copy_to_user(log->dirty_bitmap, (*memslot)->dirty_bitmap, n))
		return -EFAULT;

	if (any)
		*is_dirty = 1;
	return 0;
}
EXPORT_SYMBOL_GPL(kvm_get_dirty_log);

#else /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
/**
 * kvm_get_dirty_log_protect - get a snapshot of dirty pages
 *	and reenable dirty page tracking for the corresponding pages.
 * @kvm:	pointer to kvm instance
 * @log:	slot id and address to which we copy the log
 *
 * We need to keep it in mind that VCPU threads can write to the bitmap
 * concurrently. So, to avoid losing track of dirty pages we keep the
 * following order:
 *
 *    1. Take a snapshot of the bit and clear it if needed.
 *    2. Write protect the corresponding page.
 *    3. Copy the snapshot to the userspace.
 *    4. Upon return caller flushes TLB's if needed.
 *
 * Between 2 and 4, the guest may write to the page using the remaining TLB
 * entry.  This is not a problem because the page is reported dirty using
 * the snapshot taken before and step 4 ensures that writes done after
 * exiting to userspace will be logged for the next call.
 *
 */
static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
{
	struct kvm_memslots *slots;
	struct kvm_memory_slot *memslot;
	int i, as_id, id;
	unsigned long n;
	unsigned long *dirty_bitmap;
	unsigned long *dirty_bitmap_buffer;
	bool flush;

	/* Dirty ring tracking is exclusive to dirty log tracking */
	if (kvm->dirty_ring_size)
		return -ENXIO;

	as_id = log->slot >> 16;
	id = (u16)log->slot;
	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
		return -EINVAL;

	slots = __kvm_memslots(kvm, as_id);
	memslot = id_to_memslot(slots, id);
	if (!memslot || !memslot->dirty_bitmap)
		return -ENOENT;

	dirty_bitmap = memslot->dirty_bitmap;

	kvm_arch_sync_dirty_log(kvm, memslot);

	n = kvm_dirty_bitmap_bytes(memslot);
	flush = false;
	if (kvm->manual_dirty_log_protect) {
		/*
		 * Unlike kvm_get_dirty_log, we always return false in *flush,
		 * because no flush is needed until KVM_CLEAR_DIRTY_LOG.  There
		 * is some code duplication between this function and
		 * kvm_get_dirty_log, but hopefully all architecture
		 * transition to kvm_get_dirty_log_protect and kvm_get_dirty_log
		 * can be eliminated.
		 */
		dirty_bitmap_buffer = dirty_bitmap;
	} else {
		dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
		memset(dirty_bitmap_buffer, 0, n);

		KVM_MMU_LOCK(kvm);
		for (i = 0; i < n / sizeof(long); i++) {
			unsigned long mask;
			gfn_t offset;

			if (!dirty_bitmap[i])
				continue;

			flush = true;
			mask = xchg(&dirty_bitmap[i], 0);
			dirty_bitmap_buffer[i] = mask;

			offset = i * BITS_PER_LONG;
			kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
								offset, mask);
		}
		KVM_MMU_UNLOCK(kvm);
	}

	if (flush)
		kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);

	if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
		return -EFAULT;
	return 0;
}


/**
 * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
 * @kvm: kvm instance
 * @log: slot id and address to which we copy the log
 *
 * Steps 1-4 below provide general overview of dirty page logging. See
 * kvm_get_dirty_log_protect() function description for additional details.
 *
 * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
 * always flush the TLB (step 4) even if previous step failed  and the dirty
 * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
 * does not preclude user space subsequent dirty log read. Flushing TLB ensures
 * writes will be marked dirty for next log read.
 *
 *   1. Take a snapshot of the bit and clear it if needed.
 *   2. Write protect the corresponding page.
 *   3. Copy the snapshot to the userspace.
 *   4. Flush TLB's if needed.
 */
static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
				      struct kvm_dirty_log *log)
{
	int r;

	mutex_lock(&kvm->slots_lock);

	r = kvm_get_dirty_log_protect(kvm, log);

	mutex_unlock(&kvm->slots_lock);
	return r;
}

/**
 * kvm_clear_dirty_log_protect - clear dirty bits in the bitmap
 *	and reenable dirty page tracking for the corresponding pages.
 * @kvm:	pointer to kvm instance
 * @log:	slot id and address from which to fetch the bitmap of dirty pages
 */
static int kvm_clear_dirty_log_protect(struct kvm *kvm,
				       struct kvm_clear_dirty_log *log)
{
	struct kvm_memslots *slots;
	struct kvm_memory_slot *memslot;
	int as_id, id;
	gfn_t offset;
	unsigned long i, n;
	unsigned long *dirty_bitmap;
	unsigned long *dirty_bitmap_buffer;
	bool flush;

	/* Dirty ring tracking is exclusive to dirty log tracking */
	if (kvm->dirty_ring_size)
		return -ENXIO;

	as_id = log->slot >> 16;
	id = (u16)log->slot;
	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
		return -EINVAL;

	if (log->first_page & 63)
		return -EINVAL;

	slots = __kvm_memslots(kvm, as_id);
	memslot = id_to_memslot(slots, id);
	if (!memslot || !memslot->dirty_bitmap)
		return -ENOENT;

	dirty_bitmap = memslot->dirty_bitmap;

	n = ALIGN(log->num_pages, BITS_PER_LONG) / 8;

	if (log->first_page > memslot->npages ||
	    log->num_pages > memslot->npages - log->first_page ||
	    (log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63)))
	    return -EINVAL;

	kvm_arch_sync_dirty_log(kvm, memslot);

	flush = false;
	dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
	if (copy_from_user(dirty_bitmap_buffer, log->dirty_bitmap, n))
		return -EFAULT;

	KVM_MMU_LOCK(kvm);
	for (offset = log->first_page, i = offset / BITS_PER_LONG,
		 n = DIV_ROUND_UP(log->num_pages, BITS_PER_LONG); n--;
	     i++, offset += BITS_PER_LONG) {
		unsigned long mask = *dirty_bitmap_buffer++;
		atomic_long_t *p = (atomic_long_t *) &dirty_bitmap[i];
		if (!mask)
			continue;

		mask &= atomic_long_fetch_andnot(mask, p);

		/*
		 * mask contains the bits that really have been cleared.  This
		 * never includes any bits beyond the length of the memslot (if
		 * the length is not aligned to 64 pages), therefore it is not
		 * a problem if userspace sets them in log->dirty_bitmap.
		*/
		if (mask) {
			flush = true;
			kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
								offset, mask);
		}
	}
	KVM_MMU_UNLOCK(kvm);

	if (flush)
		kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);

	return 0;
}

static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
					struct kvm_clear_dirty_log *log)
{
	int r;

	mutex_lock(&kvm->slots_lock);

	r = kvm_clear_dirty_log_protect(kvm, log);

	mutex_unlock(&kvm->slots_lock);
	return r;
}
#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */

struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
{
	return __gfn_to_memslot(kvm_memslots(kvm), gfn);
}
EXPORT_SYMBOL_GPL(gfn_to_memslot);

struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	struct kvm_memslots *slots = kvm_vcpu_memslots(vcpu);
	u64 gen = slots->generation;
	struct kvm_memory_slot *slot;

	/*
	 * This also protects against using a memslot from a different address space,
	 * since different address spaces have different generation numbers.
	 */
	if (unlikely(gen != vcpu->last_used_slot_gen)) {
		vcpu->last_used_slot = NULL;
		vcpu->last_used_slot_gen = gen;
	}

	slot = try_get_memslot(vcpu->last_used_slot, gfn);
	if (slot)
		return slot;

	/*
	 * Fall back to searching all memslots. We purposely use
	 * search_memslots() instead of __gfn_to_memslot() to avoid
	 * thrashing the VM-wide last_used_slot in kvm_memslots.
	 */
	slot = search_memslots(slots, gfn, false);
	if (slot) {
		vcpu->last_used_slot = slot;
		return slot;
	}

	return NULL;
}

bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{
	struct kvm_memory_slot *memslot = gfn_to_memslot(kvm, gfn);

	return kvm_is_visible_memslot(memslot);
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);

bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	struct kvm_memory_slot *memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

	return kvm_is_visible_memslot(memslot);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_is_visible_gfn);

unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	struct vm_area_struct *vma;
	unsigned long addr, size;

	size = PAGE_SIZE;

	addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gfn, NULL);
	if (kvm_is_error_hva(addr))
		return PAGE_SIZE;

	mmap_read_lock(current->mm);
	vma = find_vma(current->mm, addr);
	if (!vma)
		goto out;

	size = vma_kernel_pagesize(vma);

out:
	mmap_read_unlock(current->mm);

	return size;
}

static bool memslot_is_readonly(const struct kvm_memory_slot *slot)
{
	return slot->flags & KVM_MEM_READONLY;
}

static unsigned long __gfn_to_hva_many(const struct kvm_memory_slot *slot, gfn_t gfn,
				       gfn_t *nr_pages, bool write)
{
	if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
		return KVM_HVA_ERR_BAD;

	if (memslot_is_readonly(slot) && write)
		return KVM_HVA_ERR_RO_BAD;

	if (nr_pages)
		*nr_pages = slot->npages - (gfn - slot->base_gfn);

	return __gfn_to_hva_memslot(slot, gfn);
}

static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
				     gfn_t *nr_pages)
{
	return __gfn_to_hva_many(slot, gfn, nr_pages, true);
}

unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
					gfn_t gfn)
{
	return gfn_to_hva_many(slot, gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva_memslot);

unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
	return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva);

unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	return gfn_to_hva_many(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_hva);

/*
 * Return the hva of a @gfn and the R/W attribute if possible.
 *
 * @slot: the kvm_memory_slot which contains @gfn
 * @gfn: the gfn to be translated
 * @writable: used to return the read/write attribute of the @slot if the hva
 * is valid and @writable is not NULL
 */
unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot,
				      gfn_t gfn, bool *writable)
{
	unsigned long hva = __gfn_to_hva_many(slot, gfn, NULL, false);

	if (!kvm_is_error_hva(hva) && writable)
		*writable = !memslot_is_readonly(slot);

	return hva;
}

unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable)
{
	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

	return gfn_to_hva_memslot_prot(slot, gfn, writable);
}

unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable)
{
	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

	return gfn_to_hva_memslot_prot(slot, gfn, writable);
}

static inline int check_user_page_hwpoison(unsigned long addr)
{
	int rc, flags = FOLL_HWPOISON | FOLL_WRITE;

	rc = get_user_pages(addr, 1, flags, NULL, NULL);
	return rc == -EHWPOISON;
}

/*
 * The fast path to get the writable pfn which will be stored in @pfn,
 * true indicates success, otherwise false is returned.  It's also the
 * only part that runs if we can in atomic context.
 */
static bool hva_to_pfn_fast(unsigned long addr, bool write_fault,
			    bool *writable, kvm_pfn_t *pfn)
{
	struct page *page[1];

	/*
	 * Fast pin a writable pfn only if it is a write fault request
	 * or the caller allows to map a writable pfn for a read fault
	 * request.
	 */
	if (!(write_fault || writable))
		return false;

	if (get_user_page_fast_only(addr, FOLL_WRITE, page)) {
		*pfn = page_to_pfn(page[0]);

		if (writable)
			*writable = true;
		return true;
	}

	return false;
}

/*
 * The slow path to get the pfn of the specified host virtual address,
 * 1 indicates success, -errno is returned if error is detected.
 */
static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
			   bool *writable, kvm_pfn_t *pfn)
{
	unsigned int flags = FOLL_HWPOISON;
	struct page *page;
	int npages = 0;

	might_sleep();

	if (writable)
		*writable = write_fault;

	if (write_fault)
		flags |= FOLL_WRITE;
	if (async)
		flags |= FOLL_NOWAIT;

	npages = get_user_pages_unlocked(addr, 1, &page, flags);
	if (npages != 1)
		return npages;

	/* map read fault as writable if possible */
	if (unlikely(!write_fault) && writable) {
		struct page *wpage;

		if (get_user_page_fast_only(addr, FOLL_WRITE, &wpage)) {
			*writable = true;
			put_page(page);
			page = wpage;
		}
	}
	*pfn = page_to_pfn(page);
	return npages;
}

static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
{
	if (unlikely(!(vma->vm_flags & VM_READ)))
		return false;

	if (write_fault && (unlikely(!(vma->vm_flags & VM_WRITE))))
		return false;

	return true;
}

static int kvm_try_get_pfn(kvm_pfn_t pfn)
{
	if (kvm_is_reserved_pfn(pfn))
		return 1;
	return get_page_unless_zero(pfn_to_page(pfn));
}

static int hva_to_pfn_remapped(struct vm_area_struct *vma,
			       unsigned long addr, bool write_fault,
			       bool *writable, kvm_pfn_t *p_pfn)
{
	kvm_pfn_t pfn;
	pte_t *ptep;
	spinlock_t *ptl;
	int r;

	r = follow_pte(vma->vm_mm, addr, &ptep, &ptl);
	if (r) {
		/*
		 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
		 * not call the fault handler, so do it here.
		 */
		bool unlocked = false;
		r = fixup_user_fault(current->mm, addr,
				     (write_fault ? FAULT_FLAG_WRITE : 0),
				     &unlocked);
		if (unlocked)
			return -EAGAIN;
		if (r)
			return r;

		r = follow_pte(vma->vm_mm, addr, &ptep, &ptl);
		if (r)
			return r;
	}

	if (write_fault && !pte_write(*ptep)) {
		pfn = KVM_PFN_ERR_RO_FAULT;
		goto out;
	}

	if (writable)
		*writable = pte_write(*ptep);
	pfn = pte_pfn(*ptep);

	/*
	 * Get a reference here because callers of *hva_to_pfn* and
	 * *gfn_to_pfn* ultimately call kvm_release_pfn_clean on the
	 * returned pfn.  This is only needed if the VMA has VM_MIXEDMAP
	 * set, but the kvm_try_get_pfn/kvm_release_pfn_clean pair will
	 * simply do nothing for reserved pfns.
	 *
	 * Whoever called remap_pfn_range is also going to call e.g.
	 * unmap_mapping_range before the underlying pages are freed,
	 * causing a call to our MMU notifier.
	 *
	 * Certain IO or PFNMAP mappings can be backed with valid
	 * struct pages, but be allocated without refcounting e.g.,
	 * tail pages of non-compound higher order allocations, which
	 * would then underflow the refcount when the caller does the
	 * required put_page. Don't allow those pages here.
	 */ 
	if (!kvm_try_get_pfn(pfn))
		r = -EFAULT;

out:
	pte_unmap_unlock(ptep, ptl);
	*p_pfn = pfn;

	return r;
}

/*
 * Pin guest page in memory and return its pfn.
 * @addr: host virtual address which maps memory to the guest
 * @atomic: whether this function can sleep
 * @async: whether this function need to wait IO complete if the
 *         host page is not in the memory
 * @write_fault: whether we should get a writable host page
 * @writable: whether it allows to map a writable host page for !@write_fault
 *
 * The function will map a writable host page for these two cases:
 * 1): @write_fault = true
 * 2): @write_fault = false && @writable, @writable will tell the caller
 *     whether the mapping is writable.
 */
kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
		     bool write_fault, bool *writable)
{
	struct vm_area_struct *vma;
	kvm_pfn_t pfn = 0;
	int npages, r;

	/* we can do it either atomically or asynchronously, not both */
	BUG_ON(atomic && async);

	if (hva_to_pfn_fast(addr, write_fault, writable, &pfn))
		return pfn;

	if (atomic)
		return KVM_PFN_ERR_FAULT;

	npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
	if (npages == 1)
		return pfn;

	mmap_read_lock(current->mm);
	if (npages == -EHWPOISON ||
	      (!async && check_user_page_hwpoison(addr))) {
		pfn = KVM_PFN_ERR_HWPOISON;
		goto exit;
	}

retry:
	vma = vma_lookup(current->mm, addr);

	if (vma == NULL)
		pfn = KVM_PFN_ERR_FAULT;
	else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
		r = hva_to_pfn_remapped(vma, addr, write_fault, writable, &pfn);
		if (r == -EAGAIN)
			goto retry;
		if (r < 0)
			pfn = KVM_PFN_ERR_FAULT;
	} else {
		if (async && vma_is_valid(vma, write_fault))
			*async = true;
		pfn = KVM_PFN_ERR_FAULT;
	}
exit:
	mmap_read_unlock(current->mm);
	return pfn;
}

kvm_pfn_t __gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn,
			       bool atomic, bool *async, bool write_fault,
			       bool *writable, hva_t *hva)
{
	unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);

	if (hva)
		*hva = addr;

	if (addr == KVM_HVA_ERR_RO_BAD) {
		if (writable)
			*writable = false;
		return KVM_PFN_ERR_RO_FAULT;
	}

	if (kvm_is_error_hva(addr)) {
		if (writable)
			*writable = false;
		return KVM_PFN_NOSLOT;
	}

	/* Do not map writable pfn in the readonly memslot. */
	if (writable && memslot_is_readonly(slot)) {
		*writable = false;
		writable = NULL;
	}

	return hva_to_pfn(addr, atomic, async, write_fault,
			  writable);
}
EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);

kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
		      bool *writable)
{
	return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn, false, NULL,
				    write_fault, writable, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);

kvm_pfn_t gfn_to_pfn_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
{
	return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot);

kvm_pfn_t gfn_to_pfn_memslot_atomic(const struct kvm_memory_slot *slot, gfn_t gfn)
{
	return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);

kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	return gfn_to_pfn_memslot_atomic(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_pfn_atomic);

kvm_pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
{
	return gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn);
}
EXPORT_SYMBOL_GPL(gfn_to_pfn);

kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	return gfn_to_pfn_memslot(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_pfn);

int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
			    struct page **pages, int nr_pages)
{
	unsigned long addr;
	gfn_t entry = 0;

	addr = gfn_to_hva_many(slot, gfn, &entry);
	if (kvm_is_error_hva(addr))
		return -1;

	if (entry < nr_pages)
		return 0;

	return get_user_pages_fast_only(addr, nr_pages, FOLL_WRITE, pages);
}
EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);

static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
{
	if (is_error_noslot_pfn(pfn))
		return KVM_ERR_PTR_BAD_PAGE;

	if (kvm_is_reserved_pfn(pfn)) {
		WARN_ON(1);
		return KVM_ERR_PTR_BAD_PAGE;
	}

	return pfn_to_page(pfn);
}

struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
{
	kvm_pfn_t pfn;

	pfn = gfn_to_pfn(kvm, gfn);

	return kvm_pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(gfn_to_page);

void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
{
	if (pfn == 0)
		return;

	if (dirty)
		kvm_release_pfn_dirty(pfn);
	else
		kvm_release_pfn_clean(pfn);
}

int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
{
	kvm_pfn_t pfn;
	void *hva = NULL;
	struct page *page = KVM_UNMAPPED_PAGE;

	if (!map)
		return -EINVAL;

	pfn = gfn_to_pfn(vcpu->kvm, gfn);
	if (is_error_noslot_pfn(pfn))
		return -EINVAL;

	if (pfn_valid(pfn)) {
		page = pfn_to_page(pfn);
		hva = kmap(page);
#ifdef CONFIG_HAS_IOMEM
	} else {
		hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
#endif
	}

	if (!hva)
		return -EFAULT;

	map->page = page;
	map->hva = hva;
	map->pfn = pfn;
	map->gfn = gfn;

	return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_map);

void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
{
	if (!map)
		return;

	if (!map->hva)
		return;

	if (map->page != KVM_UNMAPPED_PAGE)
		kunmap(map->page);
#ifdef CONFIG_HAS_IOMEM
	else
		memunmap(map->hva);
#endif

	if (dirty)
		kvm_vcpu_mark_page_dirty(vcpu, map->gfn);

	kvm_release_pfn(map->pfn, dirty);

	map->hva = NULL;
	map->page = NULL;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);

struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	kvm_pfn_t pfn;

	pfn = kvm_vcpu_gfn_to_pfn(vcpu, gfn);

	return kvm_pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_page);

void kvm_release_page_clean(struct page *page)
{
	WARN_ON(is_error_page(page));

	kvm_release_pfn_clean(page_to_pfn(page));
}
EXPORT_SYMBOL_GPL(kvm_release_page_clean);

void kvm_release_pfn_clean(kvm_pfn_t pfn)
{
	if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn))
		put_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_clean);

void kvm_release_page_dirty(struct page *page)
{
	WARN_ON(is_error_page(page));

	kvm_release_pfn_dirty(page_to_pfn(page));
}
EXPORT_SYMBOL_GPL(kvm_release_page_dirty);

void kvm_release_pfn_dirty(kvm_pfn_t pfn)
{
	kvm_set_pfn_dirty(pfn);
	kvm_release_pfn_clean(pfn);
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);

void kvm_set_pfn_dirty(kvm_pfn_t pfn)
{
	if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
		SetPageDirty(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);

void kvm_set_pfn_accessed(kvm_pfn_t pfn)
{
	if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
		mark_page_accessed(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);

static int next_segment(unsigned long len, int offset)
{
	if (len > PAGE_SIZE - offset)
		return PAGE_SIZE - offset;
	else
		return len;
}

static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
				 void *data, int offset, int len)
{
	int r;
	unsigned long addr;

	addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
	if (kvm_is_error_hva(addr))
		return -EFAULT;
	r = __copy_from_user(data, (void __user *)addr + offset, len);
	if (r)
		return -EFAULT;
	return 0;
}

int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
			int len)
{
	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

	return __kvm_read_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_page);

int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data,
			     int offset, int len)
{
	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

	return __kvm_read_guest_page(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_page);

int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len)
{
	gfn_t gfn = gpa >> PAGE_SHIFT;
	int seg;
	int offset = offset_in_page(gpa);
	int ret;

	while ((seg = next_segment(len, offset)) != 0) {
		ret = kvm_read_guest_page(kvm, gfn, data, offset, seg);
		if (ret < 0)
			return ret;
		offset = 0;
		len -= seg;
		data += seg;
		++gfn;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(kvm_read_guest);

int kvm_vcpu_read_guest(struct kvm_vcpu *vcpu, gpa_t gpa, void *data, unsigned long len)
{
	gfn_t gfn = gpa >> PAGE_SHIFT;
	int seg;
	int offset = offset_in_page(gpa);
	int ret;

	while ((seg = next_segment(len, offset)) != 0) {
		ret = kvm_vcpu_read_guest_page(vcpu, gfn, data, offset, seg);
		if (ret < 0)
			return ret;
		offset = 0;
		len -= seg;
		data += seg;
		++gfn;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest);

static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
			           void *data, int offset, unsigned long len)
{
	int r;
	unsigned long addr;

	addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
	if (kvm_is_error_hva(addr))
		return -EFAULT;
	pagefault_disable();
	r = __copy_from_user_inatomic(data, (void __user *)addr + offset, len);
	pagefault_enable();
	if (r)
		return -EFAULT;
	return 0;
}

int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
			       void *data, unsigned long len)
{
	gfn_t gfn = gpa >> PAGE_SHIFT;
	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
	int offset = offset_in_page(gpa);

	return __kvm_read_guest_atomic(slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);

static int __kvm_write_guest_page(struct kvm *kvm,
				  struct kvm_memory_slot *memslot, gfn_t gfn,
			          const void *data, int offset, int len)
{
	int r;
	unsigned long addr;

	addr = gfn_to_hva_memslot(memslot, gfn);
	if (kvm_is_error_hva(addr))
		return -EFAULT;
	r = __copy_to_user((void __user *)addr + offset, data, len);
	if (r)
		return -EFAULT;
	mark_page_dirty_in_slot(kvm, memslot, gfn);
	return 0;
}

int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn,
			 const void *data, int offset, int len)
{
	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);

	return __kvm_write_guest_page(kvm, slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_write_guest_page);

int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
			      const void *data, int offset, int len)
{
	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

	return __kvm_write_guest_page(vcpu->kvm, slot, gfn, data, offset, len);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);

int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
		    unsigned long len)
{
	gfn_t gfn = gpa >> PAGE_SHIFT;
	int seg;
	int offset = offset_in_page(gpa);
	int ret;

	while ((seg = next_segment(len, offset)) != 0) {
		ret = kvm_write_guest_page(kvm, gfn, data, offset, seg);
		if (ret < 0)
			return ret;
		offset = 0;
		len -= seg;
		data += seg;
		++gfn;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(kvm_write_guest);

int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
		         unsigned long len)
{
	gfn_t gfn = gpa >> PAGE_SHIFT;
	int seg;
	int offset = offset_in_page(gpa);
	int ret;

	while ((seg = next_segment(len, offset)) != 0) {
		ret = kvm_vcpu_write_guest_page(vcpu, gfn, data, offset, seg);
		if (ret < 0)
			return ret;
		offset = 0;
		len -= seg;
		data += seg;
		++gfn;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest);

static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots,
				       struct gfn_to_hva_cache *ghc,
				       gpa_t gpa, unsigned long len)
{
	int offset = offset_in_page(gpa);
	gfn_t start_gfn = gpa >> PAGE_SHIFT;
	gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT;
	gfn_t nr_pages_needed = end_gfn - start_gfn + 1;
	gfn_t nr_pages_avail;

	/* Update ghc->generation before performing any error checks. */
	ghc->generation = slots->generation;

	if (start_gfn > end_gfn) {
		ghc->hva = KVM_HVA_ERR_BAD;
		return -EINVAL;
	}

	/*
	 * If the requested region crosses two memslots, we still
	 * verify that the entire region is valid here.
	 */
	for ( ; start_gfn <= end_gfn; start_gfn += nr_pages_avail) {
		ghc->memslot = __gfn_to_memslot(slots, start_gfn);
		ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn,
					   &nr_pages_avail);
		if (kvm_is_error_hva(ghc->hva))
			return -EFAULT;
	}

	/* Use the slow path for cross page reads and writes. */
	if (nr_pages_needed == 1)
		ghc->hva += offset;
	else
		ghc->memslot = NULL;

	ghc->gpa = gpa;
	ghc->len = len;
	return 0;
}

int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
			      gpa_t gpa, unsigned long len)
{
	struct kvm_memslots *slots = kvm_memslots(kvm);
	return __kvm_gfn_to_hva_cache_init(slots, ghc, gpa, len);
}
EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);

int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
				  void *data, unsigned int offset,
				  unsigned long len)
{
	struct kvm_memslots *slots = kvm_memslots(kvm);
	int r;
	gpa_t gpa = ghc->gpa + offset;

	if (WARN_ON_ONCE(len + offset > ghc->len))
		return -EINVAL;

	if (slots->generation != ghc->generation) {
		if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
			return -EFAULT;
	}

	if (kvm_is_error_hva(ghc->hva))
		return -EFAULT;

	if (unlikely(!ghc->memslot))
		return kvm_write_guest(kvm, gpa, data, len);

	r = __copy_to_user((void __user *)ghc->hva + offset, data, len);
	if (r)
		return -EFAULT;
	mark_page_dirty_in_slot(kvm, ghc->memslot, gpa >> PAGE_SHIFT);

	return 0;
}
EXPORT_SYMBOL_GPL(kvm_write_guest_offset_cached);

int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
			   void *data, unsigned long len)
{
	return kvm_write_guest_offset_cached(kvm, ghc, data, 0, len);
}
EXPORT_SYMBOL_GPL(kvm_write_guest_cached);

int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
				 void *data, unsigned int offset,
				 unsigned long len)
{
	struct kvm_memslots *slots = kvm_memslots(kvm);
	int r;
	gpa_t gpa = ghc->gpa + offset;

	if (WARN_ON_ONCE(len + offset > ghc->len))
		return -EINVAL;

	if (slots->generation != ghc->generation) {
		if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
			return -EFAULT;
	}

	if (kvm_is_error_hva(ghc->hva))
		return -EFAULT;

	if (unlikely(!ghc->memslot))
		return kvm_read_guest(kvm, gpa, data, len);

	r = __copy_from_user(data, (void __user *)ghc->hva + offset, len);
	if (r)
		return -EFAULT;

	return 0;
}
EXPORT_SYMBOL_GPL(kvm_read_guest_offset_cached);

int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
			  void *data, unsigned long len)
{
	return kvm_read_guest_offset_cached(kvm, ghc, data, 0, len);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_cached);

int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
{
	const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));
	gfn_t gfn = gpa >> PAGE_SHIFT;
	int seg;
	int offset = offset_in_page(gpa);
	int ret;

	while ((seg = next_segment(len, offset)) != 0) {
		ret = kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
		if (ret < 0)
			return ret;
		offset = 0;
		len -= seg;
		++gfn;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(kvm_clear_guest);

void mark_page_dirty_in_slot(struct kvm *kvm,
			     const struct kvm_memory_slot *memslot,
		 	     gfn_t gfn)
{
	struct kvm_vcpu *vcpu = kvm_get_running_vcpu();

#ifdef CONFIG_HAVE_KVM_DIRTY_RING
	if (WARN_ON_ONCE(!vcpu) || WARN_ON_ONCE(vcpu->kvm != kvm))
		return;
#endif

	if (memslot && kvm_slot_dirty_track_enabled(memslot)) {
		unsigned long rel_gfn = gfn - memslot->base_gfn;
		u32 slot = (memslot->as_id << 16) | memslot->id;

		if (kvm->dirty_ring_size)
			kvm_dirty_ring_push(&vcpu->dirty_ring,
					    slot, rel_gfn);
		else
			set_bit_le(rel_gfn, memslot->dirty_bitmap);
	}
}
EXPORT_SYMBOL_GPL(mark_page_dirty_in_slot);

void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
{
	struct kvm_memory_slot *memslot;

	memslot = gfn_to_memslot(kvm, gfn);
	mark_page_dirty_in_slot(kvm, memslot, gfn);
}
EXPORT_SYMBOL_GPL(mark_page_dirty);

void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn)
{
	struct kvm_memory_slot *memslot;

	memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
	mark_page_dirty_in_slot(vcpu->kvm, memslot, gfn);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);

void kvm_sigset_activate(struct kvm_vcpu *vcpu)
{
	if (!vcpu->sigset_active)
		return;

	/*
	 * This does a lockless modification of ->real_blocked, which is fine
	 * because, only current can change ->real_blocked and all readers of
	 * ->real_blocked don't care as long ->real_blocked is always a subset
	 * of ->blocked.
	 */
	sigprocmask(SIG_SETMASK, &vcpu->sigset, &current->real_blocked);
}

void kvm_sigset_deactivate(struct kvm_vcpu *vcpu)
{
	if (!vcpu->sigset_active)
		return;

	sigprocmask(SIG_SETMASK, &current->real_blocked, NULL);
	sigemptyset(&current->real_blocked);
}

static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
{
	unsigned int old, val, grow, grow_start;

	old = val = vcpu->halt_poll_ns;
	grow_start = READ_ONCE(halt_poll_ns_grow_start);
	grow = READ_ONCE(halt_poll_ns_grow);
	if (!grow)
		goto out;

	val *= grow;
	if (val < grow_start)
		val = grow_start;

	if (val > vcpu->kvm->max_halt_poll_ns)
		val = vcpu->kvm->max_halt_poll_ns;

	vcpu->halt_poll_ns = val;
out:
	trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
}

static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
{
	unsigned int old, val, shrink, grow_start;

	old = val = vcpu->halt_poll_ns;
	shrink = READ_ONCE(halt_poll_ns_shrink);
	grow_start = READ_ONCE(halt_poll_ns_grow_start);
	if (shrink == 0)
		val = 0;
	else
		val /= shrink;

	if (val < grow_start)
		val = 0;

	vcpu->halt_poll_ns = val;
	trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
}

static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
{
	int ret = -EINTR;
	int idx = srcu_read_lock(&vcpu->kvm->srcu);

	if (kvm_arch_vcpu_runnable(vcpu)) {
		kvm_make_request(KVM_REQ_UNHALT, vcpu);
		goto out;
	}
	if (kvm_cpu_has_pending_timer(vcpu))
		goto out;
	if (signal_pending(current))
		goto out;
	if (kvm_check_request(KVM_REQ_UNBLOCK, vcpu))
		goto out;

	ret = 0;
out:
	srcu_read_unlock(&vcpu->kvm->srcu, idx);
	return ret;
}

/*
 * Block the vCPU until the vCPU is runnable, an event arrives, or a signal is
 * pending.  This is mostly used when halting a vCPU, but may also be used
 * directly for other vCPU non-runnable states, e.g. x86's Wait-For-SIPI.
 */
bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
	bool waited = false;

	vcpu->stat.generic.blocking = 1;

	kvm_arch_vcpu_blocking(vcpu);

	prepare_to_rcuwait(wait);
	for (;;) {
		set_current_state(TASK_INTERRUPTIBLE);

		if (kvm_vcpu_check_block(vcpu) < 0)
			break;

		waited = true;
		schedule();
	}
	finish_rcuwait(wait);

	kvm_arch_vcpu_unblocking(vcpu);

	vcpu->stat.generic.blocking = 0;

	return waited;
}

static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
					  ktime_t end, bool success)
{
	struct kvm_vcpu_stat_generic *stats = &vcpu->stat.generic;
	u64 poll_ns = ktime_to_ns(ktime_sub(end, start));

	++vcpu->stat.generic.halt_attempted_poll;

	if (success) {
		++vcpu->stat.generic.halt_successful_poll;

		if (!vcpu_valid_wakeup(vcpu))
			++vcpu->stat.generic.halt_poll_invalid;

		stats->halt_poll_success_ns += poll_ns;
		KVM_STATS_LOG_HIST_UPDATE(stats->halt_poll_success_hist, poll_ns);
	} else {
		stats->halt_poll_fail_ns += poll_ns;
		KVM_STATS_LOG_HIST_UPDATE(stats->halt_poll_fail_hist, poll_ns);
	}
}

/*
 * Emulate a vCPU halt condition, e.g. HLT on x86, WFI on arm, etc...  If halt
 * polling is enabled, busy wait for a short time before blocking to avoid the
 * expensive block+unblock sequence if a wake event arrives soon after the vCPU
 * is halted.
 */
void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
{
	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
	bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
	ktime_t start, cur, poll_end;
	bool waited = false;
	u64 halt_ns;

	start = cur = poll_end = ktime_get();
	if (do_halt_poll) {
		ktime_t stop = ktime_add_ns(start, vcpu->halt_poll_ns);

		do {
			/*
			 * This sets KVM_REQ_UNHALT if an interrupt
			 * arrives.
			 */
			if (kvm_vcpu_check_block(vcpu) < 0)
				goto out;
			cpu_relax();
			poll_end = cur = ktime_get();
		} while (kvm_vcpu_can_poll(cur, stop));
	}

	waited = kvm_vcpu_block(vcpu);

	cur = ktime_get();
	if (waited) {
		vcpu->stat.generic.halt_wait_ns +=
			ktime_to_ns(cur) - ktime_to_ns(poll_end);
		KVM_STATS_LOG_HIST_UPDATE(vcpu->stat.generic.halt_wait_hist,
				ktime_to_ns(cur) - ktime_to_ns(poll_end));
	}
out:
	/* The total time the vCPU was "halted", including polling time. */
	halt_ns = ktime_to_ns(cur) - ktime_to_ns(start);

	/*
	 * Note, halt-polling is considered successful so long as the vCPU was
	 * never actually scheduled out, i.e. even if the wake event arrived
	 * after of the halt-polling loop itself, but before the full wait.
	 */
	if (do_halt_poll)
		update_halt_poll_stats(vcpu, start, poll_end, !waited);

	if (halt_poll_allowed) {
		if (!vcpu_valid_wakeup(vcpu)) {
			shrink_halt_poll_ns(vcpu);
		} else if (vcpu->kvm->max_halt_poll_ns) {
			if (halt_ns <= vcpu->halt_poll_ns)
				;
			/* we had a long block, shrink polling */
			else if (vcpu->halt_poll_ns &&
				 halt_ns > vcpu->kvm->max_halt_poll_ns)
				shrink_halt_poll_ns(vcpu);
			/* we had a short halt and our poll time is too small */
			else if (vcpu->halt_poll_ns < vcpu->kvm->max_halt_poll_ns &&
				 halt_ns < vcpu->kvm->max_halt_poll_ns)
				grow_halt_poll_ns(vcpu);
		} else {
			vcpu->halt_poll_ns = 0;
		}
	}

	trace_kvm_vcpu_wakeup(halt_ns, waited, vcpu_valid_wakeup(vcpu));
}
EXPORT_SYMBOL_GPL(kvm_vcpu_halt);

bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
{
	if (__kvm_vcpu_wake_up(vcpu)) {
		WRITE_ONCE(vcpu->ready, true);
		++vcpu->stat.generic.halt_wakeup;
		return true;
	}

	return false;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_wake_up);

#ifndef CONFIG_S390
/*
 * Kick a sleeping VCPU, or a guest VCPU in guest mode, into host kernel mode.
 */
void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
	int me, cpu;

	if (kvm_vcpu_wake_up(vcpu))
		return;

	me = get_cpu();
	/*
	 * The only state change done outside the vcpu mutex is IN_GUEST_MODE
	 * to EXITING_GUEST_MODE.  Therefore the moderately expensive "should
	 * kick" check does not need atomic operations if kvm_vcpu_kick is used
	 * within the vCPU thread itself.
	 */
	if (vcpu == __this_cpu_read(kvm_running_vcpu)) {
		if (vcpu->mode == IN_GUEST_MODE)
			WRITE_ONCE(vcpu->mode, EXITING_GUEST_MODE);
		goto out;
	}

	/*
	 * Note, the vCPU could get migrated to a different pCPU at any point
	 * after kvm_arch_vcpu_should_kick(), which could result in sending an
	 * IPI to the previous pCPU.  But, that's ok because the purpose of the
	 * IPI is to force the vCPU to leave IN_GUEST_MODE, and migrating the
	 * vCPU also requires it to leave IN_GUEST_MODE.
	 */
	if (kvm_arch_vcpu_should_kick(vcpu)) {
		cpu = READ_ONCE(vcpu->cpu);
		if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
			smp_send_reschedule(cpu);
	}
out:
	put_cpu();
}
EXPORT_SYMBOL_GPL(kvm_vcpu_kick);
#endif /* !CONFIG_S390 */

int kvm_vcpu_yield_to(struct kvm_vcpu *target)
{
	struct pid *pid;
	struct task_struct *task = NULL;
	int ret = 0;

	rcu_read_lock();
	pid = rcu_dereference(target->pid);
	if (pid)
		task = get_pid_task(pid, PIDTYPE_PID);
	rcu_read_unlock();
	if (!task)
		return ret;
	ret = yield_to(task, 1);
	put_task_struct(task);

	return ret;
}
EXPORT_SYMBOL_GPL(kvm_vcpu_yield_to);

/*
 * Helper that checks whether a VCPU is eligible for directed yield.
 * Most eligible candidate to yield is decided by following heuristics:
 *
 *  (a) VCPU which has not done pl-exit or cpu relax intercepted recently
 *  (preempted lock holder), indicated by @in_spin_loop.
 *  Set at the beginning and cleared at the end of interception/PLE handler.
 *
 *  (b) VCPU which has done pl-exit/ cpu relax intercepted but did not get
 *  chance last time (mostly it has become eligible now since we have probably
 *  yielded to lockholder in last iteration. This is done by toggling
 *  @dy_eligible each time a VCPU checked for eligibility.)
 *
 *  Yielding to a recently pl-exited/cpu relax intercepted VCPU before yielding
 *  to preempted lock-holder could result in wrong VCPU selection and CPU
 *  burning. Giving priority for a potential lock-holder increases lock
 *  progress.
 *
 *  Since algorithm is based on heuristics, accessing another VCPU data without
 *  locking does not harm. It may result in trying to yield to  same VCPU, fail
 *  and continue with next VCPU and so on.
 */
static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
	bool eligible;

	eligible = !vcpu->spin_loop.in_spin_loop ||
		    vcpu->spin_loop.dy_eligible;

	if (vcpu->spin_loop.in_spin_loop)
		kvm_vcpu_set_dy_eligible(vcpu, !vcpu->spin_loop.dy_eligible);

	return eligible;
#else
	return true;
#endif
}

/*
 * Unlike kvm_arch_vcpu_runnable, this function is called outside
 * a vcpu_load/vcpu_put pair.  However, for most architectures
 * kvm_arch_vcpu_runnable does not require vcpu_load.
 */
bool __weak kvm_arch_dy_runnable(struct kvm_vcpu *vcpu)
{
	return kvm_arch_vcpu_runnable(vcpu);
}

static bool vcpu_dy_runnable(struct kvm_vcpu *vcpu)
{
	if (kvm_arch_dy_runnable(vcpu))
		return true;

#ifdef CONFIG_KVM_ASYNC_PF
	if (!list_empty_careful(&vcpu->async_pf.done))
		return true;
#endif

	return false;
}

bool __weak kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu)
{
	return false;
}

void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
{
	struct kvm *kvm = me->kvm;
	struct kvm_vcpu *vcpu;
	int last_boosted_vcpu = me->kvm->last_boosted_vcpu;
	unsigned long i;
	int yielded = 0;
	int try = 3;
	int pass;

	kvm_vcpu_set_in_spin_loop(me, true);
	/*
	 * We boost the priority of a VCPU that is runnable but not
	 * currently running, because it got preempted by something
	 * else and called schedule in __vcpu_run.  Hopefully that
	 * VCPU is holding the lock that we need and will release it.
	 * We approximate round-robin by starting at the last boosted VCPU.
	 */
	for (pass = 0; pass < 2 && !yielded && try; pass++) {
		kvm_for_each_vcpu(i, vcpu, kvm) {
			if (!pass && i <= last_boosted_vcpu) {
				i = last_boosted_vcpu;
				continue;
			} else if (pass && i > last_boosted_vcpu)
				break;
			if (!READ_ONCE(vcpu->ready))
				continue;
			if (vcpu == me)
				continue;
			if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu))
				continue;
			if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
			    !kvm_arch_dy_has_pending_interrupt(vcpu) &&
			    !kvm_arch_vcpu_in_kernel(vcpu))
				continue;
			if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
				continue;

			yielded = kvm_vcpu_yield_to(vcpu);
			if (yielded > 0) {
				kvm->last_boosted_vcpu = i;
				break;
			} else if (yielded < 0) {
				try--;
				if (!try)
					break;
			}
		}
	}
	kvm_vcpu_set_in_spin_loop(me, false);

	/* Ensure vcpu is not eligible during next spinloop */
	kvm_vcpu_set_dy_eligible(me, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);

static bool kvm_page_in_dirty_ring(struct kvm *kvm, unsigned long pgoff)
{
#ifdef CONFIG_HAVE_KVM_DIRTY_RING
	return (pgoff >= KVM_DIRTY_LOG_PAGE_OFFSET) &&
	    (pgoff < KVM_DIRTY_LOG_PAGE_OFFSET +
	     kvm->dirty_ring_size / PAGE_SIZE);
#else
	return false;
#endif
}

static vm_fault_t kvm_vcpu_fault(struct vm_fault *vmf)
{
	struct kvm_vcpu *vcpu = vmf->vma->vm_file->private_data;
	struct page *page;

	if (vmf->pgoff == 0)
		page = virt_to_page(vcpu->run);
#ifdef CONFIG_X86
	else if (vmf->pgoff == KVM_PIO_PAGE_OFFSET)
		page = virt_to_page(vcpu->arch.pio_data);
#endif
#ifdef CONFIG_KVM_MMIO
	else if (vmf->pgoff == KVM_COALESCED_MMIO_PAGE_OFFSET)
		page = virt_to_page(vcpu->kvm->coalesced_mmio_ring);
#endif
	else if (kvm_page_in_dirty_ring(vcpu->kvm, vmf->pgoff))
		page = kvm_dirty_ring_get_page(
		    &vcpu->dirty_ring,
		    vmf->pgoff - KVM_DIRTY_LOG_PAGE_OFFSET);
	else
		return kvm_arch_vcpu_fault(vcpu, vmf);
	get_page(page);
	vmf->page = page;
	return 0;
}

static const struct vm_operations_struct kvm_vcpu_vm_ops = {
	.fault = kvm_vcpu_fault,
};

static int kvm_vcpu_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct kvm_vcpu *vcpu = file->private_data;
	unsigned long pages = vma_pages(vma);

	if ((kvm_page_in_dirty_ring(vcpu->kvm, vma->vm_pgoff) ||
	     kvm_page_in_dirty_ring(vcpu->kvm, vma->vm_pgoff + pages - 1)) &&
	    ((vma->vm_flags & VM_EXEC) || !(vma->vm_flags & VM_SHARED)))
		return -EINVAL;

	vma->vm_ops = &kvm_vcpu_vm_ops;
	return 0;
}

static int kvm_vcpu_release(struct inode *inode, struct file *filp)
{
	struct kvm_vcpu *vcpu = filp->private_data;

	kvm_put_kvm(vcpu->kvm);
	return 0;
}

static const struct file_operations kvm_vcpu_fops = {
	.release        = kvm_vcpu_release,
	.unlocked_ioctl = kvm_vcpu_ioctl,
	.mmap           = kvm_vcpu_mmap,
	.llseek		= noop_llseek,
	KVM_COMPAT(kvm_vcpu_compat_ioctl),
};

/*
 * Allocates an inode for the vcpu.
 */
static int create_vcpu_fd(struct kvm_vcpu *vcpu)
{
	char name[8 + 1 + ITOA_MAX_LEN + 1];

	snprintf(name, sizeof(name), "kvm-vcpu:%d", vcpu->vcpu_id);
	return anon_inode_getfd(name, &kvm_vcpu_fops, vcpu, O_RDWR | O_CLOEXEC);
}

static void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
{
#ifdef __KVM_HAVE_ARCH_VCPU_DEBUGFS
	struct dentry *debugfs_dentry;
	char dir_name[ITOA_MAX_LEN * 2];

	if (!debugfs_initialized())
		return;

	snprintf(dir_name, sizeof(dir_name), "vcpu%d", vcpu->vcpu_id);
	debugfs_dentry = debugfs_create_dir(dir_name,
					    vcpu->kvm->debugfs_dentry);

	kvm_arch_create_vcpu_debugfs(vcpu, debugfs_dentry);
#endif
}

/*
 * Creates some virtual cpus.  Good luck creating more than one.
 */
static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
{
	int r;
	struct kvm_vcpu *vcpu;
	struct page *page;

	if (id >= KVM_MAX_VCPU_IDS)
		return -EINVAL;

	mutex_lock(&kvm->lock);
	if (kvm->created_vcpus >= kvm->max_vcpus) {
		mutex_unlock(&kvm->lock);
		return -EINVAL;
	}

	kvm->created_vcpus++;
	mutex_unlock(&kvm->lock);

	r = kvm_arch_vcpu_precreate(kvm, id);
	if (r)
		goto vcpu_decrement;

	vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
	if (!vcpu) {
		r = -ENOMEM;
		goto vcpu_decrement;
	}

	BUILD_BUG_ON(sizeof(struct kvm_run) > PAGE_SIZE);
	page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
	if (!page) {
		r = -ENOMEM;
		goto vcpu_free;
	}
	vcpu->run = page_address(page);

	kvm_vcpu_init(vcpu, kvm, id);

	r = kvm_arch_vcpu_create(vcpu);
	if (r)
		goto vcpu_free_run_page;

	if (kvm->dirty_ring_size) {
		r = kvm_dirty_ring_alloc(&vcpu->dirty_ring,
					 id, kvm->dirty_ring_size);
		if (r)
			goto arch_vcpu_destroy;
	}

	mutex_lock(&kvm->lock);
	if (kvm_get_vcpu_by_id(kvm, id)) {
		r = -EEXIST;
		goto unlock_vcpu_destroy;
	}

	vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus);
	r = xa_insert(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, GFP_KERNEL_ACCOUNT);
	BUG_ON(r == -EBUSY);
	if (r)
		goto unlock_vcpu_destroy;

	/* Fill the stats id string for the vcpu */
	snprintf(vcpu->stats_id, sizeof(vcpu->stats_id), "kvm-%d/vcpu-%d",
		 task_pid_nr(current), id);

	/* Now it's all set up, let userspace reach it */
	kvm_get_kvm(kvm);
	r = create_vcpu_fd(vcpu);
	if (r < 0) {
		xa_erase(&kvm->vcpu_array, vcpu->vcpu_idx);
		kvm_put_kvm_no_destroy(kvm);
		goto unlock_vcpu_destroy;
	}

	/*
	 * Pairs with smp_rmb() in kvm_get_vcpu.  Store the vcpu
	 * pointer before kvm->online_vcpu's incremented value.
	 */
	smp_wmb();
	atomic_inc(&kvm->online_vcpus);

	mutex_unlock(&kvm->lock);
	kvm_arch_vcpu_postcreate(vcpu);
	kvm_create_vcpu_debugfs(vcpu);
	return r;

unlock_vcpu_destroy:
	mutex_unlock(&kvm->lock);
	kvm_dirty_ring_free(&vcpu->dirty_ring);
arch_vcpu_destroy:
	kvm_arch_vcpu_destroy(vcpu);
vcpu_free_run_page:
	free_page((unsigned long)vcpu->run);
vcpu_free:
	kmem_cache_free(kvm_vcpu_cache, vcpu);
vcpu_decrement:
	mutex_lock(&kvm->lock);
	kvm->created_vcpus--;
	mutex_unlock(&kvm->lock);
	return r;
}

static int kvm_vcpu_ioctl_set_sigmask(struct kvm_vcpu *vcpu, sigset_t *sigset)
{
	if (sigset) {
		sigdelsetmask(sigset, sigmask(SIGKILL)|sigmask(SIGSTOP));
		vcpu->sigset_active = 1;
		vcpu->sigset = *sigset;
	} else
		vcpu->sigset_active = 0;
	return 0;
}

static ssize_t kvm_vcpu_stats_read(struct file *file, char __user *user_buffer,
			      size_t size, loff_t *offset)
{
	struct kvm_vcpu *vcpu = file->private_data;

	return kvm_stats_read(vcpu->stats_id, &kvm_vcpu_stats_header,
			&kvm_vcpu_stats_desc[0], &vcpu->stat,
			sizeof(vcpu->stat), user_buffer, size, offset);
}

static const struct file_operations kvm_vcpu_stats_fops = {
	.read = kvm_vcpu_stats_read,
	.llseek = noop_llseek,
};

static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
{
	int fd;
	struct file *file;
	char name[15 + ITOA_MAX_LEN + 1];

	snprintf(name, sizeof(name), "kvm-vcpu-stats:%d", vcpu->vcpu_id);

	fd = get_unused_fd_flags(O_CLOEXEC);
	if (fd < 0)
		return fd;

	file = anon_inode_getfile(name, &kvm_vcpu_stats_fops, vcpu, O_RDONLY);
	if (IS_ERR(file)) {
		put_unused_fd(fd);
		return PTR_ERR(file);
	}
	file->f_mode |= FMODE_PREAD;
	fd_install(fd, file);

	return fd;
}

static long kvm_vcpu_ioctl(struct file *filp,
			   unsigned int ioctl, unsigned long arg)
{
	struct kvm_vcpu *vcpu = filp->private_data;
	void __user *argp = (void __user *)arg;
	int r;
	struct kvm_fpu *fpu = NULL;
	struct kvm_sregs *kvm_sregs = NULL;

	if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_dead)
		return -EIO;

	if (unlikely(_IOC_TYPE(ioctl) != KVMIO))
		return -EINVAL;

	/*
	 * Some architectures have vcpu ioctls that are asynchronous to vcpu
	 * execution; mutex_lock() would break them.
	 */
	r = kvm_arch_vcpu_async_ioctl(filp, ioctl, arg);
	if (r != -ENOIOCTLCMD)
		return r;

	if (mutex_lock_killable(&vcpu->mutex))
		return -EINTR;
	switch (ioctl) {
	case KVM_RUN: {
		struct pid *oldpid;
		r = -EINVAL;
		if (arg)
			goto out;
		oldpid = rcu_access_pointer(vcpu->pid);
		if (unlikely(oldpid != task_pid(current))) {
			/* The thread running this VCPU changed. */
			struct pid *newpid;

			r = kvm_arch_vcpu_run_pid_change(vcpu);
			if (r)
				break;

			newpid = get_task_pid(current, PIDTYPE_PID);
			rcu_assign_pointer(vcpu->pid, newpid);
			if (oldpid)
				synchronize_rcu();
			put_pid(oldpid);
		}
		r = kvm_arch_vcpu_ioctl_run(vcpu);
		trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
		break;
	}
	case KVM_GET_REGS: {
		struct kvm_regs *kvm_regs;

		r = -ENOMEM;
		kvm_regs = kzalloc(sizeof(struct kvm_regs), GFP_KERNEL_ACCOUNT);
		if (!kvm_regs)
			goto out;
		r = kvm_arch_vcpu_ioctl_get_regs(vcpu, kvm_regs);
		if (r)
			goto out_free1;
		r = -EFAULT;
		if (copy_to_user(argp, kvm_regs, sizeof(struct kvm_regs)))
			goto out_free1;
		r = 0;
out_free1:
		kfree(kvm_regs);
		break;
	}
	case KVM_SET_REGS: {
		struct kvm_regs *kvm_regs;

		kvm_regs = memdup_user(argp, sizeof(*kvm_regs));
		if (IS_ERR(kvm_regs)) {
			r = PTR_ERR(kvm_regs);
			goto out;
		}
		r = kvm_arch_vcpu_ioctl_set_regs(vcpu, kvm_regs);
		kfree(kvm_regs);
		break;
	}
	case KVM_GET_SREGS: {
		kvm_sregs = kzalloc(sizeof(struct kvm_sregs),
				    GFP_KERNEL_ACCOUNT);
		r = -ENOMEM;
		if (!kvm_sregs)
			goto out;
		r = kvm_arch_vcpu_ioctl_get_sregs(vcpu, kvm_sregs);
		if (r)
			goto out;
		r = -EFAULT;
		if (copy_to_user(argp, kvm_sregs, sizeof(struct kvm_sregs)))
			goto out;
		r = 0;
		break;
	}
	case KVM_SET_SREGS: {
		kvm_sregs = memdup_user(argp, sizeof(*kvm_sregs));
		if (IS_ERR(kvm_sregs)) {
			r = PTR_ERR(kvm_sregs);
			kvm_sregs = NULL;
			goto out;
		}
		r = kvm_arch_vcpu_ioctl_set_sregs(vcpu, kvm_sregs);
		break;
	}
	case KVM_GET_MP_STATE: {
		struct kvm_mp_state mp_state;

		r = kvm_arch_vcpu_ioctl_get_mpstate(vcpu, &mp_state);
		if (r)
			goto out;
		r = -EFAULT;
		if (copy_to_user(argp, &mp_state, sizeof(mp_state)))
			goto out;
		r = 0;
		break;
	}
	case KVM_SET_MP_STATE: {
		struct kvm_mp_state mp_state;

		r = -EFAULT;
		if (copy_from_user(&mp_state, argp, sizeof(mp_state)))
			goto out;
		r = kvm_arch_vcpu_ioctl_set_mpstate(vcpu, &mp_state);
		break;
	}
	case KVM_TRANSLATE: {
		struct kvm_translation tr;

		r = -EFAULT;
		if (copy_from_user(&tr, argp, sizeof(tr)))
			goto out;
		r = kvm_arch_vcpu_ioctl_translate(vcpu, &tr);
		if (r)
			goto out;
		r = -EFAULT;
		if (copy_to_user(argp, &tr, sizeof(tr)))
			goto out;
		r = 0;
		break;
	}
	case KVM_SET_GUEST_DEBUG: {
		struct kvm_guest_debug dbg;

		r = -EFAULT;
		if (copy_from_user(&dbg, argp, sizeof(dbg)))
			goto out;
		r = kvm_arch_vcpu_ioctl_set_guest_debug(vcpu, &dbg);
		break;
	}
	case KVM_SET_SIGNAL_MASK: {
		struct kvm_signal_mask __user *sigmask_arg = argp;
		struct kvm_signal_mask kvm_sigmask;
		sigset_t sigset, *p;

		p = NULL;
		if (argp) {
			r = -EFAULT;
			if (copy_from_user(&kvm_sigmask, argp,
					   sizeof(kvm_sigmask)))
				goto out;
			r = -EINVAL;
			if (kvm_sigmask.len != sizeof(sigset))
				goto out;
			r = -EFAULT;
			if (copy_from_user(&sigset, sigmask_arg->sigset,
					   sizeof(sigset)))
				goto out;
			p = &sigset;
		}
		r = kvm_vcpu_ioctl_set_sigmask(vcpu, p);
		break;
	}
	case KVM_GET_FPU: {
		fpu = kzalloc(sizeof(struct kvm_fpu), GFP_KERNEL_ACCOUNT);
		r = -ENOMEM;
		if (!fpu)
			goto out;
		r = kvm_arch_vcpu_ioctl_get_fpu(vcpu, fpu);
		if (r)
			goto out;
		r = -EFAULT;
		if (copy_to_user(argp, fpu, sizeof(struct kvm_fpu)))
			goto out;
		r = 0;
		break;
	}
	case KVM_SET_FPU: {
		fpu = memdup_user(argp, sizeof(*fpu));
		if (IS_ERR(fpu)) {
			r = PTR_ERR(fpu);
			fpu = NULL;
			goto out;
		}
		r = kvm_arch_vcpu_ioctl_set_fpu(vcpu, fpu);
		break;
	}
	case KVM_GET_STATS_FD: {
		r = kvm_vcpu_ioctl_get_stats_fd(vcpu);
		break;
	}
	default:
		r = kvm_arch_vcpu_ioctl(filp, ioctl, arg);
	}
out:
	mutex_unlock(&vcpu->mutex);
	kfree(fpu);
	kfree(kvm_sregs);
	return r;
}

#ifdef CONFIG_KVM_COMPAT
static long kvm_vcpu_compat_ioctl(struct file *filp,
				  unsigned int ioctl, unsigned long arg)
{
	struct kvm_vcpu *vcpu = filp->private_data;
	void __user *argp = compat_ptr(arg);
	int r;

	if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_dead)
		return -EIO;

	switch (ioctl) {
	case KVM_SET_SIGNAL_MASK: {
		struct kvm_signal_mask __user *sigmask_arg = argp;
		struct kvm_signal_mask kvm_sigmask;
		sigset_t sigset;

		if (argp) {
			r = -EFAULT;
			if (copy_from_user(&kvm_sigmask, argp,
					   sizeof(kvm_sigmask)))
				goto out;
			r = -EINVAL;
			if (kvm_sigmask.len != sizeof(compat_sigset_t))
				goto out;
			r = -EFAULT;
			if (get_compat_sigset(&sigset,
					      (compat_sigset_t __user *)sigmask_arg->sigset))
				goto out;
			r = kvm_vcpu_ioctl_set_sigmask(vcpu, &sigset);
		} else
			r = kvm_vcpu_ioctl_set_sigmask(vcpu, NULL);
		break;
	}
	default:
		r = kvm_vcpu_ioctl(filp, ioctl, arg);
	}

out:
	return r;
}
#endif

static int kvm_device_mmap(struct file *filp, struct vm_area_struct *vma)
{
	struct kvm_device *dev = filp->private_data;

	if (dev->ops->mmap)
		return dev->ops->mmap(dev, vma);

	return -ENODEV;
}

static int kvm_device_ioctl_attr(struct kvm_device *dev,
				 int (*accessor)(struct kvm_device *dev,
						 struct kvm_device_attr *attr),
				 unsigned long arg)
{
	struct kvm_device_attr attr;

	if (!accessor)
		return -EPERM;

	if (copy_from_user(&attr, (void __user *)arg, sizeof(attr)))
		return -EFAULT;

	return accessor(dev, &attr);
}

static long kvm_device_ioctl(struct file *filp, unsigned int ioctl,
			     unsigned long arg)
{
	struct kvm_device *dev = filp->private_data;

	if (dev->kvm->mm != current->mm || dev->kvm->vm_dead)
		return -EIO;

	switch (ioctl) {
	case KVM_SET_DEVICE_ATTR:
		return kvm_device_ioctl_attr(dev, dev->ops->set_attr, arg);
	case KVM_GET_DEVICE_ATTR:
		return kvm_device_ioctl_attr(dev, dev->ops->get_attr, arg);
	case KVM_HAS_DEVICE_ATTR:
		return kvm_device_ioctl_attr(dev, dev->ops->has_attr, arg);
	default:
		if (dev->ops->ioctl)
			return dev->ops->ioctl(dev, ioctl, arg);

		return -ENOTTY;
	}
}

static int kvm_device_release(struct inode *inode, struct file *filp)
{
	struct kvm_device *dev = filp->private_data;
	struct kvm *kvm = dev->kvm;

	if (dev->ops->release) {
		mutex_lock(&kvm->lock);
		list_del(&dev->vm_node);
		dev->ops->release(dev);
		mutex_unlock(&kvm->lock);
	}

	kvm_put_kvm(kvm);
	return 0;
}

static const struct file_operations kvm_device_fops = {
	.unlocked_ioctl = kvm_device_ioctl,
	.release = kvm_device_release,
	KVM_COMPAT(kvm_device_ioctl),
	.mmap = kvm_device_mmap,
};

struct kvm_device *kvm_device_from_filp(struct file *filp)
{
	if (filp->f_op != &kvm_device_fops)
		return NULL;

	return filp->private_data;
}

static const struct kvm_device_ops *kvm_device_ops_table[KVM_DEV_TYPE_MAX] = {
#ifdef CONFIG_KVM_MPIC
	[KVM_DEV_TYPE_FSL_MPIC_20]	= &kvm_mpic_ops,
	[KVM_DEV_TYPE_FSL_MPIC_42]	= &kvm_mpic_ops,
#endif
};

int kvm_register_device_ops(const struct kvm_device_ops *ops, u32 type)
{
	if (type >= ARRAY_SIZE(kvm_device_ops_table))
		return -ENOSPC;

	if (kvm_device_ops_table[type] != NULL)
		return -EEXIST;

	kvm_device_ops_table[type] = ops;
	return 0;
}

void kvm_unregister_device_ops(u32 type)
{
	if (kvm_device_ops_table[type] != NULL)
		kvm_device_ops_table[type] = NULL;
}

static int kvm_ioctl_create_device(struct kvm *kvm,
				   struct kvm_create_device *cd)
{
	const struct kvm_device_ops *ops = NULL;
	struct kvm_device *dev;
	bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
	int type;
	int ret;

	if (cd->type >= ARRAY_SIZE(kvm_device_ops_table))
		return -ENODEV;

	type = array_index_nospec(cd->type, ARRAY_SIZE(kvm_device_ops_table));
	ops = kvm_device_ops_table[type];
	if (ops == NULL)
		return -ENODEV;

	if (test)
		return 0;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL_ACCOUNT);
	if (!dev)
		return -ENOMEM;

	dev->ops = ops;
	dev->kvm = kvm;

	mutex_lock(&kvm->lock);
	ret = ops->create(dev, type);
	if (ret < 0) {
		mutex_unlock(&kvm->lock);
		kfree(dev);
		return ret;
	}
	list_add(&dev->vm_node, &kvm->devices);
	mutex_unlock(&kvm->lock);

	if (ops->init)
		ops->init(dev);

	kvm_get_kvm(kvm);
	ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | O_CLOEXEC);
	if (ret < 0) {
		kvm_put_kvm_no_destroy(kvm);
		mutex_lock(&kvm->lock);
		list_del(&dev->vm_node);
		mutex_unlock(&kvm->lock);
		ops->destroy(dev);
		return ret;
	}

	cd->fd = ret;
	return 0;
}

static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
{
	switch (arg) {
	case KVM_CAP_USER_MEMORY:
	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
	case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS:
	case KVM_CAP_INTERNAL_ERROR_DATA:
#ifdef CONFIG_HAVE_KVM_MSI
	case KVM_CAP_SIGNAL_MSI:
#endif
#ifdef CONFIG_HAVE_KVM_IRQFD
	case KVM_CAP_IRQFD:
	case KVM_CAP_IRQFD_RESAMPLE:
#endif
	case KVM_CAP_IOEVENTFD_ANY_LENGTH:
	case KVM_CAP_CHECK_EXTENSION_VM:
	case KVM_CAP_ENABLE_CAP_VM:
	case KVM_CAP_HALT_POLL:
		return 1;
#ifdef CONFIG_KVM_MMIO
	case KVM_CAP_COALESCED_MMIO:
		return KVM_COALESCED_MMIO_PAGE_OFFSET;
	case KVM_CAP_COALESCED_PIO:
		return 1;
#endif
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
	case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2:
		return KVM_DIRTY_LOG_MANUAL_CAPS;
#endif
#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
	case KVM_CAP_IRQ_ROUTING:
		return KVM_MAX_IRQ_ROUTES;
#endif
#if KVM_ADDRESS_SPACE_NUM > 1
	case KVM_CAP_MULTI_ADDRESS_SPACE:
		return KVM_ADDRESS_SPACE_NUM;
#endif
	case KVM_CAP_NR_MEMSLOTS:
		return KVM_USER_MEM_SLOTS;
	case KVM_CAP_DIRTY_LOG_RING:
#ifdef CONFIG_HAVE_KVM_DIRTY_RING
		return KVM_DIRTY_RING_MAX_ENTRIES * sizeof(struct kvm_dirty_gfn);
#else
		return 0;
#endif
	case KVM_CAP_BINARY_STATS_FD:
	case KVM_CAP_SYSTEM_EVENT_DATA:
		return 1;
	default:
		break;
	}
	return kvm_vm_ioctl_check_extension(kvm, arg);
}

static int kvm_vm_ioctl_enable_dirty_log_ring(struct kvm *kvm, u32 size)
{
	int r;

	if (!KVM_DIRTY_LOG_PAGE_OFFSET)
		return -EINVAL;

	/* the size should be power of 2 */
	if (!size || (size & (size - 1)))
		return -EINVAL;

	/* Should be bigger to keep the reserved entries, or a page */
	if (size < kvm_dirty_ring_get_rsvd_entries() *
	    sizeof(struct kvm_dirty_gfn) || size < PAGE_SIZE)
		return -EINVAL;

	if (size > KVM_DIRTY_RING_MAX_ENTRIES *
	    sizeof(struct kvm_dirty_gfn))
		return -E2BIG;

	/* We only allow it to set once */
	if (kvm->dirty_ring_size)
		return -EINVAL;

	mutex_lock(&kvm->lock);

	if (kvm->created_vcpus) {
		/* We don't allow to change this value after vcpu created */
		r = -EINVAL;
	} else {
		kvm->dirty_ring_size = size;
		r = 0;
	}

	mutex_unlock(&kvm->lock);
	return r;
}

static int kvm_vm_ioctl_reset_dirty_pages(struct kvm *kvm)
{
	unsigned long i;
	struct kvm_vcpu *vcpu;
	int cleared = 0;

	if (!kvm->dirty_ring_size)
		return -EINVAL;

	mutex_lock(&kvm->slots_lock);

	kvm_for_each_vcpu(i, vcpu, kvm)
		cleared += kvm_dirty_ring_reset(vcpu->kvm, &vcpu->dirty_ring);

	mutex_unlock(&kvm->slots_lock);

	if (cleared)
		kvm_flush_remote_tlbs(kvm);

	return cleared;
}

int __attribute__((weak)) kvm_vm_ioctl_enable_cap(struct kvm *kvm,
						  struct kvm_enable_cap *cap)
{
	return -EINVAL;
}

static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
					   struct kvm_enable_cap *cap)
{
	switch (cap->cap) {
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
	case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: {
		u64 allowed_options = KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE;

		if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE)
			allowed_options = KVM_DIRTY_LOG_MANUAL_CAPS;

		if (cap->flags || (cap->args[0] & ~allowed_options))
			return -EINVAL;
		kvm->manual_dirty_log_protect = cap->args[0];
		return 0;
	}
#endif
	case KVM_CAP_HALT_POLL: {
		if (cap->flags || cap->args[0] != (unsigned int)cap->args[0])
			return -EINVAL;

		kvm->max_halt_poll_ns = cap->args[0];
		return 0;
	}
	case KVM_CAP_DIRTY_LOG_RING:
		return kvm_vm_ioctl_enable_dirty_log_ring(kvm, cap->args[0]);
	default:
		return kvm_vm_ioctl_enable_cap(kvm, cap);
	}
}

static ssize_t kvm_vm_stats_read(struct file *file, char __user *user_buffer,
			      size_t size, loff_t *offset)
{
	struct kvm *kvm = file->private_data;

	return kvm_stats_read(kvm->stats_id, &kvm_vm_stats_header,
				&kvm_vm_stats_desc[0], &kvm->stat,
				sizeof(kvm->stat), user_buffer, size, offset);
}

static const struct file_operations kvm_vm_stats_fops = {
	.read = kvm_vm_stats_read,
	.llseek = noop_llseek,
};

static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
{
	int fd;
	struct file *file;

	fd = get_unused_fd_flags(O_CLOEXEC);
	if (fd < 0)
		return fd;

	file = anon_inode_getfile("kvm-vm-stats",
			&kvm_vm_stats_fops, kvm, O_RDONLY);
	if (IS_ERR(file)) {
		put_unused_fd(fd);
		return PTR_ERR(file);
	}
	file->f_mode |= FMODE_PREAD;
	fd_install(fd, file);

	return fd;
}

static long kvm_vm_ioctl(struct file *filp,
			   unsigned int ioctl, unsigned long arg)
{
	struct kvm *kvm = filp->private_data;
	void __user *argp = (void __user *)arg;
	int r;

	if (kvm->mm != current->mm || kvm->vm_dead)
		return -EIO;
	switch (ioctl) {
	case KVM_CREATE_VCPU:
		r = kvm_vm_ioctl_create_vcpu(kvm, arg);
		break;
	case KVM_ENABLE_CAP: {
		struct kvm_enable_cap cap;

		r = -EFAULT;
		if (copy_from_user(&cap, argp, sizeof(cap)))
			goto out;
		r = kvm_vm_ioctl_enable_cap_generic(kvm, &cap);
		break;
	}
	case KVM_SET_USER_MEMORY_REGION: {
		struct kvm_userspace_memory_region kvm_userspace_mem;

		r = -EFAULT;
		if (copy_from_user(&kvm_userspace_mem, argp,
						sizeof(kvm_userspace_mem)))
			goto out;

		r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);
		break;
	}
	case KVM_GET_DIRTY_LOG: {
		struct kvm_dirty_log log;

		r = -EFAULT;
		if (copy_from_user(&log, argp, sizeof(log)))
			goto out;
		r = kvm_vm_ioctl_get_dirty_log(kvm, &log);
		break;
	}
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
	case KVM_CLEAR_DIRTY_LOG: {
		struct kvm_clear_dirty_log log;

		r = -EFAULT;
		if (copy_from_user(&log, argp, sizeof(log)))
			goto out;
		r = kvm_vm_ioctl_clear_dirty_log(kvm, &log);
		break;
	}
#endif
#ifdef CONFIG_KVM_MMIO
	case KVM_REGISTER_COALESCED_MMIO: {
		struct kvm_coalesced_mmio_zone zone;

		r = -EFAULT;
		if (copy_from_user(&zone, argp, sizeof(zone)))
			goto out;
		r = kvm_vm_ioctl_register_coalesced_mmio(kvm, &zone);
		break;
	}
	case KVM_UNREGISTER_COALESCED_MMIO: {
		struct kvm_coalesced_mmio_zone zone;

		r = -EFAULT;
		if (copy_from_user(&zone, argp, sizeof(zone)))
			goto out;
		r = kvm_vm_ioctl_unregister_coalesced_mmio(kvm, &zone);
		break;
	}
#endif
	case KVM_IRQFD: {
		struct kvm_irqfd data;

		r = -EFAULT;
		if (copy_from_user(&data, argp, sizeof(data)))
			goto out;
		r = kvm_irqfd(kvm, &data);
		break;
	}
	case KVM_IOEVENTFD: {
		struct kvm_ioeventfd data;

		r = -EFAULT;
		if (copy_from_user(&data, argp, sizeof(data)))
			goto out;
		r = kvm_ioeventfd(kvm, &data);
		break;
	}
#ifdef CONFIG_HAVE_KVM_MSI
	case KVM_SIGNAL_MSI: {
		struct kvm_msi msi;

		r = -EFAULT;
		if (copy_from_user(&msi, argp, sizeof(msi)))
			goto out;
		r = kvm_send_userspace_msi(kvm, &msi);
		break;
	}
#endif
#ifdef __KVM_HAVE_IRQ_LINE
	case KVM_IRQ_LINE_STATUS:
	case KVM_IRQ_LINE: {
		struct kvm_irq_level irq_event;

		r = -EFAULT;
		if (copy_from_user(&irq_event, argp, sizeof(irq_event)))
			goto out;

		r = kvm_vm_ioctl_irq_line(kvm, &irq_event,
					ioctl == KVM_IRQ_LINE_STATUS);
		if (r)
			goto out;

		r = -EFAULT;
		if (ioctl == KVM_IRQ_LINE_STATUS) {
			if (copy_to_user(argp, &irq_event, sizeof(irq_event)))
				goto out;
		}

		r = 0;
		break;
	}
#endif
#ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
	case KVM_SET_GSI_ROUTING: {
		struct kvm_irq_routing routing;
		struct kvm_irq_routing __user *urouting;
		struct kvm_irq_routing_entry *entries = NULL;

		r = -EFAULT;
		if (copy_from_user(&routing, argp, sizeof(routing)))
			goto out;
		r = -EINVAL;
		if (!kvm_arch_can_set_irq_routing(kvm))
			goto out;
		if (routing.nr > KVM_MAX_IRQ_ROUTES)
			goto out;
		if (routing.flags)
			goto out;
		if (routing.nr) {
			urouting = argp;
			entries = vmemdup_user(urouting->entries,
					       array_size(sizeof(*entries),
							  routing.nr));
			if (IS_ERR(entries)) {
				r = PTR_ERR(entries);
				goto out;
			}
		}
		r = kvm_set_irq_routing(kvm, entries, routing.nr,
					routing.flags);
		kvfree(entries);
		break;
	}
#endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
	case KVM_CREATE_DEVICE: {
		struct kvm_create_device cd;

		r = -EFAULT;
		if (copy_from_user(&cd, argp, sizeof(cd)))
			goto out;

		r = kvm_ioctl_create_device(kvm, &cd);
		if (r)
			goto out;

		r = -EFAULT;
		if (copy_to_user(argp, &cd, sizeof(cd)))
			goto out;

		r = 0;
		break;
	}
	case KVM_CHECK_EXTENSION:
		r = kvm_vm_ioctl_check_extension_generic(kvm, arg);
		break;
	case KVM_RESET_DIRTY_RINGS:
		r = kvm_vm_ioctl_reset_dirty_pages(kvm);
		break;
	case KVM_GET_STATS_FD:
		r = kvm_vm_ioctl_get_stats_fd(kvm);
		break;
	default:
		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
	}
out:
	return r;
}

#ifdef CONFIG_KVM_COMPAT
struct compat_kvm_dirty_log {
	__u32 slot;
	__u32 padding1;
	union {
		compat_uptr_t dirty_bitmap; /* one bit per page */
		__u64 padding2;
	};
};

struct compat_kvm_clear_dirty_log {
	__u32 slot;
	__u32 num_pages;
	__u64 first_page;
	union {
		compat_uptr_t dirty_bitmap; /* one bit per page */
		__u64 padding2;
	};
};

static long kvm_vm_compat_ioctl(struct file *filp,
			   unsigned int ioctl, unsigned long arg)
{
	struct kvm *kvm = filp->private_data;
	int r;

	if (kvm->mm != current->mm || kvm->vm_dead)
		return -EIO;
	switch (ioctl) {
#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
	case KVM_CLEAR_DIRTY_LOG: {
		struct compat_kvm_clear_dirty_log compat_log;
		struct kvm_clear_dirty_log log;

		if (copy_from_user(&compat_log, (void __user *)arg,
				   sizeof(compat_log)))
			return -EFAULT;
		log.slot	 = compat_log.slot;
		log.num_pages	 = compat_log.num_pages;
		log.first_page	 = compat_log.first_page;
		log.padding2	 = compat_log.padding2;
		log.dirty_bitmap = compat_ptr(compat_log.dirty_bitmap);

		r = kvm_vm_ioctl_clear_dirty_log(kvm, &log);
		break;
	}
#endif
	case KVM_GET_DIRTY_LOG: {
		struct compat_kvm_dirty_log compat_log;
		struct kvm_dirty_log log;

		if (copy_from_user(&compat_log, (void __user *)arg,
				   sizeof(compat_log)))
			return -EFAULT;
		log.slot	 = compat_log.slot;
		log.padding1	 = compat_log.padding1;
		log.padding2	 = compat_log.padding2;
		log.dirty_bitmap = compat_ptr(compat_log.dirty_bitmap);

		r = kvm_vm_ioctl_get_dirty_log(kvm, &log);
		break;
	}
	default:
		r = kvm_vm_ioctl(filp, ioctl, arg);
	}
	return r;
}
#endif

static const struct file_operations kvm_vm_fops = {
	.release        = kvm_vm_release,
	.unlocked_ioctl = kvm_vm_ioctl,
	.llseek		= noop_llseek,
	KVM_COMPAT(kvm_vm_compat_ioctl),
};

bool file_is_kvm(struct file *file)
{
	return file && file->f_op == &kvm_vm_fops;
}
EXPORT_SYMBOL_GPL(file_is_kvm);

static int kvm_dev_ioctl_create_vm(unsigned long type)
{
	int r;
	struct kvm *kvm;
	struct file *file;

	kvm = kvm_create_vm(type);
	if (IS_ERR(kvm))
		return PTR_ERR(kvm);
#ifdef CONFIG_KVM_MMIO
	r = kvm_coalesced_mmio_init(kvm);
	if (r < 0)
		goto put_kvm;
#endif
	r = get_unused_fd_flags(O_CLOEXEC);
	if (r < 0)
		goto put_kvm;

	snprintf(kvm->stats_id, sizeof(kvm->stats_id),
			"kvm-%d", task_pid_nr(current));

	file = anon_inode_getfile("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
	if (IS_ERR(file)) {
		put_unused_fd(r);
		r = PTR_ERR(file);
		goto put_kvm;
	}

	/*
	 * Don't call kvm_put_kvm anymore at this point; file->f_op is
	 * already set, with ->release() being kvm_vm_release().  In error
	 * cases it will be called by the final fput(file) and will take
	 * care of doing kvm_put_kvm(kvm).
	 */
	if (kvm_create_vm_debugfs(kvm, r) < 0) {
		put_unused_fd(r);
		fput(file);
		return -ENOMEM;
	}
	kvm_uevent_notify_change(KVM_EVENT_CREATE_VM, kvm);

	fd_install(r, file);
	return r;

put_kvm:
	kvm_put_kvm(kvm);
	return r;
}

static long kvm_dev_ioctl(struct file *filp,
			  unsigned int ioctl, unsigned long arg)
{
	long r = -EINVAL;

	switch (ioctl) {
	case KVM_GET_API_VERSION:
		if (arg)
			goto out;
		r = KVM_API_VERSION;
		break;
	case KVM_CREATE_VM:
		r = kvm_dev_ioctl_create_vm(arg);
		break;
	case KVM_CHECK_EXTENSION:
		r = kvm_vm_ioctl_check_extension_generic(NULL, arg);
		break;
	case KVM_GET_VCPU_MMAP_SIZE:
		if (arg)
			goto out;
		r = PAGE_SIZE;     /* struct kvm_run */
#ifdef CONFIG_X86
		r += PAGE_SIZE;    /* pio data page */
#endif
#ifdef CONFIG_KVM_MMIO
		r += PAGE_SIZE;    /* coalesced mmio ring page */
#endif
		break;
	case KVM_TRACE_ENABLE:
	case KVM_TRACE_PAUSE:
	case KVM_TRACE_DISABLE:
		r = -EOPNOTSUPP;
		break;
	default:
		return kvm_arch_dev_ioctl(filp, ioctl, arg);
	}
out:
	return r;
}

static struct file_operations kvm_chardev_ops = {
	.unlocked_ioctl = kvm_dev_ioctl,
	.llseek		= noop_llseek,
	KVM_COMPAT(kvm_dev_ioctl),
};

static struct miscdevice kvm_dev = {
	KVM_MINOR,
	"kvm",
	&kvm_chardev_ops,
};

static void hardware_enable_nolock(void *junk)
{
	int cpu = raw_smp_processor_id();
	int r;

	if (cpumask_test_cpu(cpu, cpus_hardware_enabled))
		return;

	cpumask_set_cpu(cpu, cpus_hardware_enabled);

	r = kvm_arch_hardware_enable();

	if (r) {
		cpumask_clear_cpu(cpu, cpus_hardware_enabled);
		atomic_inc(&hardware_enable_failed);
		pr_info("kvm: enabling virtualization on CPU%d failed\n", cpu);
	}
}

static int kvm_starting_cpu(unsigned int cpu)
{
	raw_spin_lock(&kvm_count_lock);
	if (kvm_usage_count)
		hardware_enable_nolock(NULL);
	raw_spin_unlock(&kvm_count_lock);
	return 0;
}

static void hardware_disable_nolock(void *junk)
{
	int cpu = raw_smp_processor_id();

	if (!cpumask_test_cpu(cpu, cpus_hardware_enabled))
		return;
	cpumask_clear_cpu(cpu, cpus_hardware_enabled);
	kvm_arch_hardware_disable();
}

static int kvm_dying_cpu(unsigned int cpu)
{
	raw_spin_lock(&kvm_count_lock);
	if (kvm_usage_count)
		hardware_disable_nolock(NULL);
	raw_spin_unlock(&kvm_count_lock);
	return 0;
}

static void hardware_disable_all_nolock(void)
{
	BUG_ON(!kvm_usage_count);

	kvm_usage_count--;
	if (!kvm_usage_count)
		on_each_cpu(hardware_disable_nolock, NULL, 1);
}

static void hardware_disable_all(void)
{
	raw_spin_lock(&kvm_count_lock);
	hardware_disable_all_nolock();
	raw_spin_unlock(&kvm_count_lock);
}

static int hardware_enable_all(void)
{
	int r = 0;

	raw_spin_lock(&kvm_count_lock);

	kvm_usage_count++;
	if (kvm_usage_count == 1) {
		atomic_set(&hardware_enable_failed, 0);
		on_each_cpu(hardware_enable_nolock, NULL, 1);

		if (atomic_read(&hardware_enable_failed)) {
			hardware_disable_all_nolock();
			r = -EBUSY;
		}
	}

	raw_spin_unlock(&kvm_count_lock);

	return r;
}

static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
		      void *v)
{
	/*
	 * Some (well, at least mine) BIOSes hang on reboot if
	 * in vmx root mode.
	 *
	 * And Intel TXT required VMX off for all cpu when system shutdown.
	 */
	pr_info("kvm: exiting hardware virtualization\n");
	kvm_rebooting = true;
	on_each_cpu(hardware_disable_nolock, NULL, 1);
	return NOTIFY_OK;
}

static struct notifier_block kvm_reboot_notifier = {
	.notifier_call = kvm_reboot,
	.priority = 0,
};

static void kvm_io_bus_destroy(struct kvm_io_bus *bus)
{
	int i;

	for (i = 0; i < bus->dev_count; i++) {
		struct kvm_io_device *pos = bus->range[i].dev;

		kvm_iodevice_destructor(pos);
	}
	kfree(bus);
}

static inline int kvm_io_bus_cmp(const struct kvm_io_range *r1,
				 const struct kvm_io_range *r2)
{
	gpa_t addr1 = r1->addr;
	gpa_t addr2 = r2->addr;

	if (addr1 < addr2)
		return -1;

	/* If r2->len == 0, match the exact address.  If r2->len != 0,
	 * accept any overlapping write.  Any order is acceptable for
	 * overlapping ranges, because kvm_io_bus_get_first_dev ensures
	 * we process all of them.
	 */
	if (r2->len) {
		addr1 += r1->len;
		addr2 += r2->len;
	}

	if (addr1 > addr2)
		return 1;

	return 0;
}

static int kvm_io_bus_sort_cmp(const void *p1, const void *p2)
{
	return kvm_io_bus_cmp(p1, p2);
}

static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus,
			     gpa_t addr, int len)
{
	struct kvm_io_range *range, key;
	int off;

	key = (struct kvm_io_range) {
		.addr = addr,
		.len = len,
	};

	range = bsearch(&key, bus->range, bus->dev_count,
			sizeof(struct kvm_io_range), kvm_io_bus_sort_cmp);
	if (range == NULL)
		return -ENOENT;

	off = range - bus->range;

	while (off > 0 && kvm_io_bus_cmp(&key, &bus->range[off-1]) == 0)
		off--;

	return off;
}

static int __kvm_io_bus_write(struct kvm_vcpu *vcpu, struct kvm_io_bus *bus,
			      struct kvm_io_range *range, const void *val)
{
	int idx;

	idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
	if (idx < 0)
		return -EOPNOTSUPP;

	while (idx < bus->dev_count &&
		kvm_io_bus_cmp(range, &bus->range[idx]) == 0) {
		if (!kvm_iodevice_write(vcpu, bus->range[idx].dev, range->addr,
					range->len, val))
			return idx;
		idx++;
	}

	return -EOPNOTSUPP;
}

/* kvm_io_bus_write - called under kvm->slots_lock */
int kvm_io_bus_write(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
		     int len, const void *val)
{
	struct kvm_io_bus *bus;
	struct kvm_io_range range;
	int r;

	range = (struct kvm_io_range) {
		.addr = addr,
		.len = len,
	};

	bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
	if (!bus)
		return -ENOMEM;
	r = __kvm_io_bus_write(vcpu, bus, &range, val);
	return r < 0 ? r : 0;
}
EXPORT_SYMBOL_GPL(kvm_io_bus_write);

/* kvm_io_bus_write_cookie - called under kvm->slots_lock */
int kvm_io_bus_write_cookie(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx,
			    gpa_t addr, int len, const void *val, long cookie)
{
	struct kvm_io_bus *bus;
	struct kvm_io_range range;

	range = (struct kvm_io_range) {
		.addr = addr,
		.len = len,
	};

	bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
	if (!bus)
		return -ENOMEM;

	/* First try the device referenced by cookie. */
	if ((cookie >= 0) && (cookie < bus->dev_count) &&
	    (kvm_io_bus_cmp(&range, &bus->range[cookie]) == 0))
		if (!kvm_iodevice_write(vcpu, bus->range[cookie].dev, addr, len,
					val))
			return cookie;

	/*
	 * cookie contained garbage; fall back to search and return the
	 * correct cookie value.
	 */
	return __kvm_io_bus_write(vcpu, bus, &range, val);
}

static int __kvm_io_bus_read(struct kvm_vcpu *vcpu, struct kvm_io_bus *bus,
			     struct kvm_io_range *range, void *val)
{
	int idx;

	idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
	if (idx < 0)
		return -EOPNOTSUPP;

	while (idx < bus->dev_count &&
		kvm_io_bus_cmp(range, &bus->range[idx]) == 0) {
		if (!kvm_iodevice_read(vcpu, bus->range[idx].dev, range->addr,
				       range->len, val))
			return idx;
		idx++;
	}

	return -EOPNOTSUPP;
}

/* kvm_io_bus_read - called under kvm->slots_lock */
int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
		    int len, void *val)
{
	struct kvm_io_bus *bus;
	struct kvm_io_range range;
	int r;

	range = (struct kvm_io_range) {
		.addr = addr,
		.len = len,
	};

	bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu);
	if (!bus)
		return -ENOMEM;
	r = __kvm_io_bus_read(vcpu, bus, &range, val);
	return r < 0 ? r : 0;
}

/* Caller must hold slots_lock. */
int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
			    int len, struct kvm_io_device *dev)
{
	int i;
	struct kvm_io_bus *new_bus, *bus;
	struct kvm_io_range range;

	bus = kvm_get_bus(kvm, bus_idx);
	if (!bus)
		return -ENOMEM;

	/* exclude ioeventfd which is limited by maximum fd */
	if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
		return -ENOSPC;

	new_bus = kmalloc(struct_size(bus, range, bus->dev_count + 1),
			  GFP_KERNEL_ACCOUNT);
	if (!new_bus)
		return -ENOMEM;

	range = (struct kvm_io_range) {
		.addr = addr,
		.len = len,
		.dev = dev,
	};

	for (i = 0; i < bus->dev_count; i++)
		if (kvm_io_bus_cmp(&bus->range[i], &range) > 0)
			break;

	memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
	new_bus->dev_count++;
	new_bus->range[i] = range;
	memcpy(new_bus->range + i + 1, bus->range + i,
		(bus->dev_count - i) * sizeof(struct kvm_io_range));
	rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
	synchronize_srcu_expedited(&kvm->srcu);
	kfree(bus);

	return 0;
}

int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
			      struct kvm_io_device *dev)
{
	int i, j;
	struct kvm_io_bus *new_bus, *bus;

	lockdep_assert_held(&kvm->slots_lock);

	bus = kvm_get_bus(kvm, bus_idx);
	if (!bus)
		return 0;

	for (i = 0; i < bus->dev_count; i++) {
		if (bus->range[i].dev == dev) {
			break;
		}
	}

	if (i == bus->dev_count)
		return 0;

	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
			  GFP_KERNEL_ACCOUNT);
	if (new_bus) {
		memcpy(new_bus, bus, struct_size(bus, range, i));
		new_bus->dev_count--;
		memcpy(new_bus->range + i, bus->range + i + 1,
				flex_array_size(new_bus, range, new_bus->dev_count - i));
	}

	rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
	synchronize_srcu_expedited(&kvm->srcu);

	/* Destroy the old bus _after_ installing the (null) bus. */
	if (!new_bus) {
		pr_err("kvm: failed to shrink bus, removing it completely\n");
		for (j = 0; j < bus->dev_count; j++) {
			if (j == i)
				continue;
			kvm_iodevice_destructor(bus->range[j].dev);
		}
	}

	kfree(bus);
	return new_bus ? 0 : -ENOMEM;
}

struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx,
					 gpa_t addr)
{
	struct kvm_io_bus *bus;
	int dev_idx, srcu_idx;
	struct kvm_io_device *iodev = NULL;

	srcu_idx = srcu_read_lock(&kvm->srcu);

	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
	if (!bus)
		goto out_unlock;

	dev_idx = kvm_io_bus_get_first_dev(bus, addr, 1);
	if (dev_idx < 0)
		goto out_unlock;

	iodev = bus->range[dev_idx].dev;

out_unlock:
	srcu_read_unlock(&kvm->srcu, srcu_idx);

	return iodev;
}
EXPORT_SYMBOL_GPL(kvm_io_bus_get_dev);

static int kvm_debugfs_open(struct inode *inode, struct file *file,
			   int (*get)(void *, u64 *), int (*set)(void *, u64),
			   const char *fmt)
{
	struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
					  inode->i_private;

	/*
	 * The debugfs files are a reference to the kvm struct which
        * is still valid when kvm_destroy_vm is called.  kvm_get_kvm_safe
        * avoids the race between open and the removal of the debugfs directory.
	 */
	if (!kvm_get_kvm_safe(stat_data->kvm))
		return -ENOENT;

	if (simple_attr_open(inode, file, get,
		    kvm_stats_debugfs_mode(stat_data->desc) & 0222
		    ? set : NULL,
		    fmt)) {
		kvm_put_kvm(stat_data->kvm);
		return -ENOMEM;
	}

	return 0;
}

static int kvm_debugfs_release(struct inode *inode, struct file *file)
{
	struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
					  inode->i_private;

	simple_attr_release(inode, file);
	kvm_put_kvm(stat_data->kvm);

	return 0;
}

static int kvm_get_stat_per_vm(struct kvm *kvm, size_t offset, u64 *val)
{
	*val = *(u64 *)((void *)(&kvm->stat) + offset);

	return 0;
}

static int kvm_clear_stat_per_vm(struct kvm *kvm, size_t offset)
{
	*(u64 *)((void *)(&kvm->stat) + offset) = 0;

	return 0;
}

static int kvm_get_stat_per_vcpu(struct kvm *kvm, size_t offset, u64 *val)
{
	unsigned long i;
	struct kvm_vcpu *vcpu;

	*val = 0;

	kvm_for_each_vcpu(i, vcpu, kvm)
		*val += *(u64 *)((void *)(&vcpu->stat) + offset);

	return 0;
}

static int kvm_clear_stat_per_vcpu(struct kvm *kvm, size_t offset)
{
	unsigned long i;
	struct kvm_vcpu *vcpu;

	kvm_for_each_vcpu(i, vcpu, kvm)
		*(u64 *)((void *)(&vcpu->stat) + offset) = 0;

	return 0;
}

static int kvm_stat_data_get(void *data, u64 *val)
{
	int r = -EFAULT;
	struct kvm_stat_data *stat_data = (struct kvm_stat_data *)data;

	switch (stat_data->kind) {
	case KVM_STAT_VM:
		r = kvm_get_stat_per_vm(stat_data->kvm,
					stat_data->desc->desc.offset, val);
		break;
	case KVM_STAT_VCPU:
		r = kvm_get_stat_per_vcpu(stat_data->kvm,
					  stat_data->desc->desc.offset, val);
		break;
	}

	return r;
}

static int kvm_stat_data_clear(void *data, u64 val)
{
	int r = -EFAULT;
	struct kvm_stat_data *stat_data = (struct kvm_stat_data *)data;

	if (val)
		return -EINVAL;

	switch (stat_data->kind) {
	case KVM_STAT_VM:
		r = kvm_clear_stat_per_vm(stat_data->kvm,
					  stat_data->desc->desc.offset);
		break;
	case KVM_STAT_VCPU:
		r = kvm_clear_stat_per_vcpu(stat_data->kvm,
					    stat_data->desc->desc.offset);
		break;
	}

	return r;
}

static int kvm_stat_data_open(struct inode *inode, struct file *file)
{
	__simple_attr_check_format("%llu\n", 0ull);
	return kvm_debugfs_open(inode, file, kvm_stat_data_get,
				kvm_stat_data_clear, "%llu\n");
}

static const struct file_operations stat_fops_per_vm = {
	.owner = THIS_MODULE,
	.open = kvm_stat_data_open,
	.release = kvm_debugfs_release,
	.read = simple_attr_read,
	.write = simple_attr_write,
	.llseek = no_llseek,
};

static int vm_stat_get(void *_offset, u64 *val)
{
	unsigned offset = (long)_offset;
	struct kvm *kvm;
	u64 tmp_val;

	*val = 0;
	mutex_lock(&kvm_lock);
	list_for_each_entry(kvm, &vm_list, vm_list) {
		kvm_get_stat_per_vm(kvm, offset, &tmp_val);
		*val += tmp_val;
	}
	mutex_unlock(&kvm_lock);
	return 0;
}

static int vm_stat_clear(void *_offset, u64 val)
{
	unsigned offset = (long)_offset;
	struct kvm *kvm;

	if (val)
		return -EINVAL;

	mutex_lock(&kvm_lock);
	list_for_each_entry(kvm, &vm_list, vm_list) {
		kvm_clear_stat_per_vm(kvm, offset);
	}
	mutex_unlock(&kvm_lock);

	return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(vm_stat_fops, vm_stat_get, vm_stat_clear, "%llu\n");
DEFINE_SIMPLE_ATTRIBUTE(vm_stat_readonly_fops, vm_stat_get, NULL, "%llu\n");

static int vcpu_stat_get(void *_offset, u64 *val)
{
	unsigned offset = (long)_offset;
	struct kvm *kvm;
	u64 tmp_val;

	*val = 0;
	mutex_lock(&kvm_lock);
	list_for_each_entry(kvm, &vm_list, vm_list) {
		kvm_get_stat_per_vcpu(kvm, offset, &tmp_val);
		*val += tmp_val;
	}
	mutex_unlock(&kvm_lock);
	return 0;
}

static int vcpu_stat_clear(void *_offset, u64 val)
{
	unsigned offset = (long)_offset;
	struct kvm *kvm;

	if (val)
		return -EINVAL;

	mutex_lock(&kvm_lock);
	list_for_each_entry(kvm, &vm_list, vm_list) {
		kvm_clear_stat_per_vcpu(kvm, offset);
	}
	mutex_unlock(&kvm_lock);

	return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(vcpu_stat_fops, vcpu_stat_get, vcpu_stat_clear,
			"%llu\n");
DEFINE_SIMPLE_ATTRIBUTE(vcpu_stat_readonly_fops, vcpu_stat_get, NULL, "%llu\n");

static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
{
	struct kobj_uevent_env *env;
	unsigned long long created, active;

	if (!kvm_dev.this_device || !kvm)
		return;

	mutex_lock(&kvm_lock);
	if (type == KVM_EVENT_CREATE_VM) {
		kvm_createvm_count++;
		kvm_active_vms++;
	} else if (type == KVM_EVENT_DESTROY_VM) {
		kvm_active_vms--;
	}
	created = kvm_createvm_count;
	active = kvm_active_vms;
	mutex_unlock(&kvm_lock);

	env = kzalloc(sizeof(*env), GFP_KERNEL_ACCOUNT);
	if (!env)
		return;

	add_uevent_var(env, "CREATED=%llu", created);
	add_uevent_var(env, "COUNT=%llu", active);

	if (type == KVM_EVENT_CREATE_VM) {
		add_uevent_var(env, "EVENT=create");
		kvm->userspace_pid = task_pid_nr(current);
	} else if (type == KVM_EVENT_DESTROY_VM) {
		add_uevent_var(env, "EVENT=destroy");
	}
	add_uevent_var(env, "PID=%d", kvm->userspace_pid);

	if (!IS_ERR(kvm->debugfs_dentry)) {
		char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);

		if (p) {
			tmp = dentry_path_raw(kvm->debugfs_dentry, p, PATH_MAX);
			if (!IS_ERR(tmp))
				add_uevent_var(env, "STATS_PATH=%s", tmp);
			kfree(p);
		}
	}
	/* no need for checks, since we are adding at most only 5 keys */
	env->envp[env->envp_idx++] = NULL;
	kobject_uevent_env(&kvm_dev.this_device->kobj, KOBJ_CHANGE, env->envp);
	kfree(env);
}

static void kvm_init_debug(void)
{
	const struct file_operations *fops;
	const struct _kvm_stats_desc *pdesc;
	int i;

	kvm_debugfs_dir = debugfs_create_dir("kvm", NULL);

	for (i = 0; i < kvm_vm_stats_header.num_desc; ++i) {
		pdesc = &kvm_vm_stats_desc[i];
		if (kvm_stats_debugfs_mode(pdesc) & 0222)
			fops = &vm_stat_fops;
		else
			fops = &vm_stat_readonly_fops;
		debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
				kvm_debugfs_dir,
				(void *)(long)pdesc->desc.offset, fops);
	}

	for (i = 0; i < kvm_vcpu_stats_header.num_desc; ++i) {
		pdesc = &kvm_vcpu_stats_desc[i];
		if (kvm_stats_debugfs_mode(pdesc) & 0222)
			fops = &vcpu_stat_fops;
		else
			fops = &vcpu_stat_readonly_fops;
		debugfs_create_file(pdesc->name, kvm_stats_debugfs_mode(pdesc),
				kvm_debugfs_dir,
				(void *)(long)pdesc->desc.offset, fops);
	}
}

static int kvm_suspend(void)
{
	if (kvm_usage_count)
		hardware_disable_nolock(NULL);
	return 0;
}

static void kvm_resume(void)
{
	if (kvm_usage_count) {
		lockdep_assert_not_held(&kvm_count_lock);
		hardware_enable_nolock(NULL);
	}
}

static struct syscore_ops kvm_syscore_ops = {
	.suspend = kvm_suspend,
	.resume = kvm_resume,
};

static inline
struct kvm_vcpu *preempt_notifier_to_vcpu(struct preempt_notifier *pn)
{
	return container_of(pn, struct kvm_vcpu, preempt_notifier);
}

static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
{
	struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);

	WRITE_ONCE(vcpu->preempted, false);
	WRITE_ONCE(vcpu->ready, false);

	__this_cpu_write(kvm_running_vcpu, vcpu);
	kvm_arch_sched_in(vcpu, cpu);
	kvm_arch_vcpu_load(vcpu, cpu);
}

static void kvm_sched_out(struct preempt_notifier *pn,
			  struct task_struct *next)
{
	struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);

	if (current->on_rq) {
		WRITE_ONCE(vcpu->preempted, true);
		WRITE_ONCE(vcpu->ready, true);
	}
	kvm_arch_vcpu_put(vcpu);
	__this_cpu_write(kvm_running_vcpu, NULL);
}

/**
 * kvm_get_running_vcpu - get the vcpu running on the current CPU.
 *
 * We can disable preemption locally around accessing the per-CPU variable,
 * and use the resolved vcpu pointer after enabling preemption again,
 * because even if the current thread is migrated to another CPU, reading
 * the per-CPU value later will give us the same value as we update the
 * per-CPU variable in the preempt notifier handlers.
 */
struct kvm_vcpu *kvm_get_running_vcpu(void)
{
	struct kvm_vcpu *vcpu;

	preempt_disable();
	vcpu = __this_cpu_read(kvm_running_vcpu);
	preempt_enable();

	return vcpu;
}
EXPORT_SYMBOL_GPL(kvm_get_running_vcpu);

/**
 * kvm_get_running_vcpus - get the per-CPU array of currently running vcpus.
 */
struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
{
        return &kvm_running_vcpu;
}

#ifdef CONFIG_GUEST_PERF_EVENTS
static unsigned int kvm_guest_state(void)
{
	struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
	unsigned int state;

	if (!kvm_arch_pmi_in_guest(vcpu))
		return 0;

	state = PERF_GUEST_ACTIVE;
	if (!kvm_arch_vcpu_in_kernel(vcpu))
		state |= PERF_GUEST_USER;

	return state;
}

static unsigned long kvm_guest_get_ip(void)
{
	struct kvm_vcpu *vcpu = kvm_get_running_vcpu();

	/* Retrieving the IP must be guarded by a call to kvm_guest_state(). */
	if (WARN_ON_ONCE(!kvm_arch_pmi_in_guest(vcpu)))
		return 0;

	return kvm_arch_vcpu_get_ip(vcpu);
}

static struct perf_guest_info_callbacks kvm_guest_cbs = {
	.state			= kvm_guest_state,
	.get_ip			= kvm_guest_get_ip,
	.handle_intel_pt_intr	= NULL,
};

void kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void))
{
	kvm_guest_cbs.handle_intel_pt_intr = pt_intr_handler;
	perf_register_guest_info_callbacks(&kvm_guest_cbs);
}
void kvm_unregister_perf_callbacks(void)
{
	perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
}
#endif

struct kvm_cpu_compat_check {
	void *opaque;
	int *ret;
};

static void check_processor_compat(void *data)
{
	struct kvm_cpu_compat_check *c = data;

	*c->ret = kvm_arch_check_processor_compat(c->opaque);
}

int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
		  struct module *module)
{
	struct kvm_cpu_compat_check c;
	int r;
	int cpu;

	r = kvm_arch_init(opaque);
	if (r)
		goto out_fail;

	/*
	 * kvm_arch_init makes sure there's at most one caller
	 * for architectures that support multiple implementations,
	 * like intel and amd on x86.
	 * kvm_arch_init must be called before kvm_irqfd_init to avoid creating
	 * conflicts in case kvm is already setup for another implementation.
	 */
	r = kvm_irqfd_init();
	if (r)
		goto out_irqfd;

	if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
		r = -ENOMEM;
		goto out_free_0;
	}

	r = kvm_arch_hardware_setup(opaque);
	if (r < 0)
		goto out_free_1;

	c.ret = &r;
	c.opaque = opaque;
	for_each_online_cpu(cpu) {
		smp_call_function_single(cpu, check_processor_compat, &c, 1);
		if (r < 0)
			goto out_free_2;
	}

	r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_STARTING, "kvm/cpu:starting",
				      kvm_starting_cpu, kvm_dying_cpu);
	if (r)
		goto out_free_2;
	register_reboot_notifier(&kvm_reboot_notifier);

	/* A kmem cache lets us meet the alignment requirements of fx_save. */
	if (!vcpu_align)
		vcpu_align = __alignof__(struct kvm_vcpu);
	kvm_vcpu_cache =
		kmem_cache_create_usercopy("kvm_vcpu", vcpu_size, vcpu_align,
					   SLAB_ACCOUNT,
					   offsetof(struct kvm_vcpu, arch),
					   offsetofend(struct kvm_vcpu, stats_id)
					   - offsetof(struct kvm_vcpu, arch),
					   NULL);
	if (!kvm_vcpu_cache) {
		r = -ENOMEM;
		goto out_free_3;
	}

	for_each_possible_cpu(cpu) {
		if (!alloc_cpumask_var_node(&per_cpu(cpu_kick_mask, cpu),
					    GFP_KERNEL, cpu_to_node(cpu))) {
			r = -ENOMEM;
			goto out_free_4;
		}
	}

	r = kvm_async_pf_init();
	if (r)
		goto out_free_5;

	kvm_chardev_ops.owner = module;

	r = misc_register(&kvm_dev);
	if (r) {
		pr_err("kvm: misc device register failed\n");
		goto out_unreg;
	}

	register_syscore_ops(&kvm_syscore_ops);

	kvm_preempt_ops.sched_in = kvm_sched_in;
	kvm_preempt_ops.sched_out = kvm_sched_out;

	kvm_init_debug();

	r = kvm_vfio_ops_init();
	WARN_ON(r);

	return 0;

out_unreg:
	kvm_async_pf_deinit();
out_free_5:
	for_each_possible_cpu(cpu)
		free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
out_free_4:
	kmem_cache_destroy(kvm_vcpu_cache);
out_free_3:
	unregister_reboot_notifier(&kvm_reboot_notifier);
	cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
out_free_2:
	kvm_arch_hardware_unsetup();
out_free_1:
	free_cpumask_var(cpus_hardware_enabled);
out_free_0:
	kvm_irqfd_exit();
out_irqfd:
	kvm_arch_exit();
out_fail:
	return r;
}
EXPORT_SYMBOL_GPL(kvm_init);

void kvm_exit(void)
{
	int cpu;

	debugfs_remove_recursive(kvm_debugfs_dir);
	misc_deregister(&kvm_dev);
	for_each_possible_cpu(cpu)
		free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
	kmem_cache_destroy(kvm_vcpu_cache);
	kvm_async_pf_deinit();
	unregister_syscore_ops(&kvm_syscore_ops);
	unregister_reboot_notifier(&kvm_reboot_notifier);
	cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
	on_each_cpu(hardware_disable_nolock, NULL, 1);
	kvm_arch_hardware_unsetup();
	kvm_arch_exit();
	kvm_irqfd_exit();
	free_cpumask_var(cpus_hardware_enabled);
	kvm_vfio_ops_exit();
}
EXPORT_SYMBOL_GPL(kvm_exit);

struct kvm_vm_worker_thread_context {
	struct kvm *kvm;
	struct task_struct *parent;
	struct completion init_done;
	kvm_vm_thread_fn_t thread_fn;
	uintptr_t data;
	int err;
};

static int kvm_vm_worker_thread(void *context)
{
	/*
	 * The init_context is allocated on the stack of the parent thread, so
	 * we have to locally copy anything that is needed beyond initialization
	 */
	struct kvm_vm_worker_thread_context *init_context = context;
	struct task_struct *parent;
	struct kvm *kvm = init_context->kvm;
	kvm_vm_thread_fn_t thread_fn = init_context->thread_fn;
	uintptr_t data = init_context->data;
	int err;

	err = kthread_park(current);
	/* kthread_park(current) is never supposed to return an error */
	WARN_ON(err != 0);
	if (err)
		goto init_complete;

	err = cgroup_attach_task_all(init_context->parent, current);
	if (err) {
		kvm_err("%s: cgroup_attach_task_all failed with err %d\n",
			__func__, err);
		goto init_complete;
	}

	set_user_nice(current, task_nice(init_context->parent));

init_complete:
	init_context->err = err;
	complete(&init_context->init_done);
	init_context = NULL;

	if (err)
		goto out;

	/* Wait to be woken up by the spawner before proceeding. */
	kthread_parkme();

	if (!kthread_should_stop())
		err = thread_fn(kvm, data);

out:
	/*
	 * Move kthread back to its original cgroup to prevent it lingering in
	 * the cgroup of the VM process, after the latter finishes its
	 * execution.
	 *
	 * kthread_stop() waits on the 'exited' completion condition which is
	 * set in exit_mm(), via mm_release(), in do_exit(). However, the
	 * kthread is removed from the cgroup in the cgroup_exit() which is
	 * called after the exit_mm(). This causes the kthread_stop() to return
	 * before the kthread actually quits the cgroup.
	 */
	rcu_read_lock();
	parent = rcu_dereference(current->real_parent);
	get_task_struct(parent);
	rcu_read_unlock();
	cgroup_attach_task_all(parent, current);
	put_task_struct(parent);

	return err;
}

int kvm_vm_create_worker_thread(struct kvm *kvm, kvm_vm_thread_fn_t thread_fn,
				uintptr_t data, const char *name,
				struct task_struct **thread_ptr)
{
	struct kvm_vm_worker_thread_context init_context = {};
	struct task_struct *thread;

	*thread_ptr = NULL;
	init_context.kvm = kvm;
	init_context.parent = current;
	init_context.thread_fn = thread_fn;
	init_context.data = data;
	init_completion(&init_context.init_done);

	thread = kthread_run(kvm_vm_worker_thread, &init_context,
			     "%s-%d", name, task_pid_nr(current));
	if (IS_ERR(thread))
		return PTR_ERR(thread);

	/* kthread_run is never supposed to return NULL */
	WARN_ON(thread == NULL);

	wait_for_completion(&init_context.init_done);

	if (!init_context.err)
		*thread_ptr = thread;

	return init_context.err;
}